Twin - Knowledge

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in a decreased twinning propensity in species such as giraffes, elephants, and hippopotami. Despite this adaptation, a case of rare monozygotic twinning has been documented in two elephant calves at the Bandipur Tiger Reserve in Karnataka, India. Chief Veterinarian of the Wildlife Trust of India, NVK Ashraf, in response to the twinning event, wrote that "in species that invest longer time in producing a baby, taking care of two twin calves will be difficult. Therefore, the incidence of twinning will be comparatively less."Ashraf's insight not only illuminates the rarity of twinning among large mammals in the natural world, but directs our attention to the increased twinning propensity of animals under human care. This increased twinning propensity is thought to be either caused by random mutation facilitated by genetic drift, or the positive selection of the "twinning" trait in human-controlled conditions. Due to the removal of natural predators and unpredictable environmental conditions with the increase of human-provided food and medical care, species residing in nature reserves, zoos, etc., carry an increased likelihood of reversing their naturally-selected traits that have been passed on for generations. When considering this phenomenon in relation to twinning, larger mammals not commonly associated with high twinning propensities can perhaps produce twins as an adaptive response to their human-controlled environment. Additionally, the high twinning propensity in species is thought to be positively correlated with the infant mortality rate of the reproducing organism's environment (Rickard, 2022, p.2). Thus if a species lives in a controlled environment with a low infant mortality rate, the frequency of the "twinning trait" could increase, leading to a higher likelihood of producing twin offspring. In the case of the monozygotic twin calves in India, their existence could be connected to a new, positively selected adaptation of twinning attributed to species living under human care (Ward, 2014, p.7-11).

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produce twins because of their small size and insect-based diet (Varella, 2018). This is because their small size indicates shorter gestation periods and the rapid maturation of offspring, resulting in a shorter lifespan where organisms are rapidly replaced by newer generations. The smaller size of the cebidae genus also makes these species more susceptible to predators, thus triggering the heightened pace of birth, maturation, reproduction, and death. Meanwhile, cebidae's insectivorous existence can be correlated with this genus's heightened ability to reproduce, as more resources become available, more organisms can take advantage of these resources. Thus, monkeys that are smaller and have more access to food, such as the cebidae genus, have the ability to produce more offspring at a quicker pace. In terms of dizygotic twinning, it has been observed that older mothers within the cebidae genus have a higher chance of producing twins than those at the beginning stages of their fertility. Despite their access to resources, the cebidae genus has a high mortality rate attributed to their size, meaning that in order to "keep up" their quickened lifecycle, they must produce an excess of offspring in ensuring generational survival. The positively-selected adaptation of twinning counteracts the genus's high mortality rate by giving older mothers the chance to produce more than one offspring. This not only increases the likelihood that one or more of these offspring will reach reproductive maturity, but gives the mother a chance to birth at least one viable offspring despite their age. Due to their short life cycles, the cebidae genus is more inclined to produce dizygotic twins in their older reproductive years, thus signaling that the trait of high twinning propensity is one that is passed down in service of this genus's survival.

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higher twinning propensities. In his study on the evolution of litter size in bats, Garbino discovered that the vespertilionidae genus has higher twinning propensities as a result of their high roosting habitats. When tracked phylogenetically, scientists determined that the common ancestor of bats carried a higher twinning propensity which was then lost, and picked up again, eighteen times in evolutionary history. While other bat subfamilies such as Myotinae and Murinae inevitably lost the twinning trait, the family Vespertilionidae retained a high trait frequency due to mutation and environmental conditions that triggered natural selection. The height and exposed nature of Vespertilionidae's roosting locations resulted in a sharp increase in species mortality rate. Natural selection offsets these dangers by positively selecting high twinning propensity, resulting in not only Vespertilionidae's increased ability to produce twins but the increased likelihood of the genus's reproductive survival. This means that despite the family's high exposure to factors that would seemingly increase mortality rates, Vespertilionidae counteracts their environmental conditions through the evolutionary adaptation of dizygotic twins.

806: 737: 713: 42: 1270:. There is controversy on the best method of delivery where the first twin is head first and the second is not. When the first twin is not head down a caesarean section is often recommended. It is estimated that 75% of twin pregnancies in the United States were delivered by caesarean section in 2008. In comparison, the rate of caesarean section for all pregnancies in the general population varies between 14% and 40%. In twins that share the same placenta, delivery may be considered at 36 weeks. For twins who are born early, there is insufficient evidence for or against placing preterm stable twins in the same cot or incubator (co-bedding). 1593:" (Horton, 2016). Additionally, armadillos have also been known to produce monozygotic twins, sometimes birthing two sets of identical twins during one reproductive cycle. Monozygotic twinning in armadillos functions as an evolutionary adaptation preventing inbreeding. Once an armadillo offspring enters its reproductive stage, the organism is forced to leave the nest in search of its mate, rather than mating with its siblings. Not only does monozygotic twinning dissuade from armadillo siblings inbreeding, but by forcing migration from the nest, this adaptation ensures the increased 1518: 408: 463:, caused by differing environmental influences throughout their lives. Epigenetics refers to the level of activity of any particular gene. A gene may become switched on, switched off, or could become partially switched on or off in an individual. This epigenetic modification is triggered by environmental events. Monozygotic twins can have markedly different epigenetic profiles. A study of 80 pairs of monozygotic twins ranging in age from three to 74 showed that the youngest twins have relatively few 1211: 907:, there were 40 twins and 2 triplets per 1000 births. Twenty-six percent of twins were monozygotic. The incidence of multiple births, which was about five times higher than that observed in any western population, was significantly lower than that of other ethnic groups, who live in the hot and humid climate of the southern part of the country. The incidence of multiple births was related to maternal age but did not bear any association to the climate or prevalence of 227: 1405: 521: 1504:

isolate them from the social environment surrounding them. Idioglossia has been found to be a rare occurrence and the attention of scientists has shifted away from this idea. However, there are researchers and scientists that say cryptophasia or idioglossia is not a rare phenomenon. Current research is looking into the impacts of a richer social environment for these twins to stimulate their development of language.

1063: 712: 736: 90:('non-identical' or 'fraternal'), meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell. Since identical twins develop from one zygote, they will share the same sex, while fraternal twins may or may not. In very rare cases twins can have the same mother and different fathers ( 235: 1443:. In their seminal publication, Gabbett, Fisk and colleagues documented a second case of sesquizygosis and presented molecular evidence of the phenomenon. The reported twins shared 100% of their maternal chromosomes and 78% of their paternal genomic information. The authors presented evidence that two 1419:

In 2007, a study reported a case of a pair of living twins, which shared an identical set of maternal chromosomes, while each having a distinct set of paternal chromosomes, albeit from the same man, and thus they most likely share half of their father's genetic makeup. The twins were both found to be

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could be responsible for the high ratio of twins in the area. His theory was rejected by Brazilian scientists who had studied twins living in Linha São Pedro; they suggested genetic factors within that community as a more likely explanation. A high twinning rate has also been observed in other places

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A chimera is an ordinary person or animal except that some of their parts actually came from their twin or from the mother. A chimera may arise either from monozygotic twin fetuses (where it would be impossible to detect), or from dizygotic fetuses, which can be identified by chromosomal comparisons

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Monozygotic twins are genetically nearly identical and they are the same chromosomal sex unless there has been a mutation during development. The children of monozygotic twins test genetically as half-siblings (or full siblings, if a pair of monozygotic twins reproduces with another pair or with the

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Due to the increased parental investment provided for their offspring, larger mammals with longer life spans have slower reproductive cycles and tend to birth only one offspring at a time. This commonly repeated behavior in larger mammals evolved as a fixed, naturally-selected adaptation, resulting

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is defined as a private language that is usually invented by young children, specifically twins. Another term to describe what some people call "twin talk" is cryptophasia where a language is developed by twins that only they can understand. The increased focused communication between two twins may

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Conjoined twins (or the once-commonly used term "siamese") are monozygotic twins whose bodies are joined during pregnancy. This occurs when the zygote starts to split after day 12 following fertilization and fails to separate completely. This condition occurs in about 1 in 50,000 human pregnancies.

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There were 836,104 deliveries of babies in Hesse over the 15-year study period, including 11,740 twin pregnancies, of which only 4,110 met the inclusion criteria and hence were examined in the study. The excluded twin pregnancies were in cases of (1) delivery before 34 weeks of gestation; (2) when

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species, scientists Guilherme Siniciato Terra Garbino (2021) and Marco Varella (2018) have proven that smaller species experiencing infertility in old age and/or unstable habits as a result of increased predation or human interference can experience have undergone natural selection in gaining even

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occurs when a fetus dies after 20 weeks of gestation. There are two types of stillbirth, including intrauterine death and intrapartum death. Intrauterine death occurs when a baby dies during late pregnancy. Intrapartum death, which is more common, occurs when a baby dies while the mother is giving

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known to occur in human populations. Polymorphisms appeared in 2 of the 33 million comparisons, leading the researchers to extrapolate that the blood cells of monozygotic twins may have on the order of one DNA-sequence difference for every 12 million nucleotides, which would imply hundreds of

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The prevalence of dizygotic twinning in monkeys is thought to be an "insurance adaptation" for mothers reproducing at the end of their fertile years. While dizygotic twinning has been observed in species such as gorillas and chimpanzees, monkeys in the cebidae genus are found to be more likely to

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The study stated that the occurrence of complications "was found to be more likely with increasing twin-to-twin delivery time interval" and suggested that the interval be kept short, though it noted that the study did not examine causes of complications and did not control for factors such as the

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The likelihood of a single fertilization resulting in monozygotic twins is uniformly distributed in all populations around the world. This is in marked contrast to dizygotic twinning, which ranges from about six per thousand births in Japan (almost similar to the rate of identical twins, which is

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Jonsson, Hakon; Magnusdottir, Erna; Eggertsson, Hannes P.; Stefansson, Olafur A.; Arnadottir, Gudny A.; Eiriksson, Ogmundur; Zink, Florian; Helgason, Einar A.; Jonsdottir, Ingileif; Gylfason, Arnaldur; Jonasdottir, Adalbjorg; Jonasdottir, Aslaug; Beyter, Doruk; Steingrimsdottir, Thora; Norddahl,

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Among non-twin births, male singletons are slightly (about five percent) more common than female singletons. The rates for singletons vary slightly by country. For example, the sex ratio of birth in the US is 1.05 males/female, while it is 1.07 males/female in Italy. However, males are also more

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Among monozygotic twins, in extremely rare cases, twins have been born with different sexes (one male, one female). When monozygotic twins are born with different sexes it is because of chromosomal defects. The probability of this is so small that multiples having different sexes is universally

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The degree of separation of the twins in utero depends on if and when they split into two zygotes. Dizygotic twins were always two zygotes. Monozygotic twins split into two zygotes at some time very early in the pregnancy. The timing of this separation determines the chorionicity (the number of

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differences. The number of epigenetic differences increases with age. Fifty-year-old twins had over three times the epigenetic difference of three-year-old twins. Twins who had spent their lives apart (such as those adopted by two different sets of parents at birth) had the greatest difference.

173:. There is no known genetic link for identical twinning. Other factors that increase the odds of having fraternal twins include maternal age, fertility drugs and other fertility treatments, nutrition, and prior births. Some women intentionally turn to fertility drugs in order to conceive twins. 1151:

A very rare type of parasitic twinning is one where a single viable twin is endangered when the other zygote becomes cancerous, or "molar". This means that the molar zygote's cellular division continues unchecked, resulting in a cancerous growth that overtakes the viable fetus. Typically, this

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Multiple pregnancies are much less likely to carry to full term than single births, with twin pregnancies lasting on average 37 weeks, three weeks less than full term. Women who have a family history of fraternal twins have a higher chance of producing fraternal twins themselves, as there is a

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Species with small physicalities and quick reproductive cycles carry high twinning propensities as a result of increased predation and high mortality rates. As scientists continue to study the origin of dizygotic twinning in the animal kingdom, many have turned to species that demonstrated an

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differences across the entire genome. The mutations producing the differences detected in this study would have occurred during embryonic cell-division (after the point of fertilization). If they occur early in fetal development, they will be present in a very large proportion of body cells.

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in the animal kingdom are rare but have been recorded on a number of occasions. In 2016, a C-section of an Irish Wolfhound revealed identical twin puppies sharing a singular placenta. South African scientists, who were called in to study the identical twins wrote that... "To the best of our

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There have also been cases in which twins are born a number of days apart. Possibly the worldwide record for the duration of the time gap between the first and the second delivery was the birth of twins 97 days apart in Cologne, Germany, the first of which was born on November 17, 2018.

1482:). If the split occurs later than this time period, the twins risk being conjoined. There is no DNA-based zygosity test that can determine if twins are indeed mirror image. The term "mirror image" is used because the twins, when facing each other, appear as matching reflections. 481:

suggesting that identical twins may not be quite as identical as previously thought. The four-year study of monozygotic (identical) twins and their extended families revealed that these twins have genetic differences that begin in the early stages of embryonic development.

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exams sometimes reveal an "extra" fetus, which fails to develop and instead disintegrates and vanishes in the uterus. There are several reasons for the "vanishing" fetus, including it being embodied or absorbed by the other fetus, placenta or the mother. This is known as

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Mirror image twins result when a fertilized egg splits later in the embryonic stage than normal timing, around day 9–12. This type of twinning could exhibit characteristics with reversed asymmetry, such as opposite dominant handedness, dental structure, or even organs

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in twins compared to single-born children. These studies have converged on the notion that there is a greater rate of delay in language development in twins compared to their single-born counterparts. The reasons for this phenomenon are still in question; however,

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birth. The cause of stillbirth is often unknown, but the rate of babies who are stillborn is higher in twins and multiple births. Caesareans or inductions are advised after 38 weeks of pregnancy for twins, because the risk of stillbirth increases after this time.

536:. Non-conjoined monozygotic twins form up to day 14 of embryonic development, but when twinning occurs after 14 days, the twins will likely be conjoined. Furthermore, there can be various degrees of shared environment of twins in the womb, potentially leading to 4827:

Souter, Vivienne L; Parisi, Melissa A; Nyholt, Dale R; Kapur, Raj P; Henders, Anjali K; Opheim, Kent E; Gunther, Daniel F; Mitchell, Michael E; Glass, Ian A; Montgomery, Grant W (2007). "A case of true hermaphroditism reveals an unusual mechanism of twinning".

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twins can develop differently, due to their genes being differently activated. More unusual are "semi-identical twins", also known as "sesquizygotic". As of 2019, only two cases have been reported. These "half-identical twins" are hypothesized to occur when an

419:. In 18–30% of monozygotic twins each fetus has a separate placenta and a separate amniotic sac. A small number (1–2%) of monozygotic twins share the same placenta and amniotic sac. Fraternal twins each have their own placenta and own amniotic sac. 318:

Dizygotic twins are also more common for older mothers, with twinning rates doubling in mothers over the age of 35. With the advent of technologies and techniques to assist women in getting pregnant, the rate of fraternals has increased markedly.

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Another abnormality that can result in monozygotic twins of different sexes is if the egg is fertilized by a male sperm but during cell division only the X chromosome is duplicated. This results in one normal male (XY) and one female with

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Studies show that there is a genetic proclivity for dizygotic twinning. However, it is only the mother who has any effect on the chances of having such twins; there is no known mechanism for a father to cause the release of more than one

1188:. More than half of twins are born weighing less than 5.5 pounds (2.5 kg), while the average birth weight of a healthy baby should be around 6–8 pounds (3–4 kg). This is largely due to the fact that twins are typically born 1034:

Researchers suspect that as many as 1 in 8 pregnancies start out as multiples, but only a single fetus is brought to full term, because the other fetus has died very early in the pregnancy and has not been detected or recorded. Early

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mothers (who exclude dairy from their diets) are one-fifth as likely to have twins as vegetarian or omnivore mothers, and concluded that "Genotypes favoring elevated IGF and diets including dairy products, especially in areas where

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cycle, identical to the ovulation of dizygotic twins, they produce more than two offspring. Species such as sheep, goats, and deer have a higher propensity for dizygotic twinning, meaning that they carry a higher frequency of the

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Bieber, Frederick R.; Walter E. Nance; Cynthia C. Morton; Judith A. Brown; Fay O. Redwine; Robert L. Jordan and T. Mohanakumar (1981-08-14). "Genetic Studies of an Acardiac Monster: Evidence of Polar Body Twinning in Man".

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The vast majority of twins are either dizygotic (fraternal) or monozygotic (identical). In humans dizygotic twins occur more often than monozygotic twins. Less common variants are discussed further down the article.

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placentae) and amniocity (the number of sacs) of the pregnancy. Dichorionic twins either never divided (i.e.: were dizygotic) or they divided within the first 4 days. Monoamnionic twins divide after the first week.

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Monozygotic twins who share a placenta can develop twin-to-twin transfusion syndrome. This condition means that blood from one twin is being diverted into the other twin. One twin, the 'donor' twin, is small and

2092:"My father is an identical twin and my husband's grandfather is a fraternal twin. Does this increase our changes of having twins, or is the genetic trait only on the mother's side and only for fraternal twins?" 1078:

Most conjoined twins are now evaluated for surgery to attempt to separate them into separate functional bodies. The degree of difficulty rises if a vital organ or structure is shared between twins, such as the

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Am J Med Genet C Semin Med Genet. 2009 May 15;151C(2):136-41. Not really identical: epigenetic differences in monozygotic twins and implications for twin studies in psychiatry. Haque FN, Gottesman II, Wong

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Non-human dizygotic twinning is a common phenomenon in multiple animal species, including cats, dogs, cattle, bats, chimpanzees, and deer. This should not be confused with an animal's ability to produce a

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Twin studies are utilized in an attempt to determine how much of a particular trait is attributable to either genetics or environmental influence. These studies compare monozygotic and dizygotic twins for

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Women undergoing certain fertility treatments may have a greater chance of dizygotic multiple births. In the United States it has been estimated that by 2011 36% of twin births resulted from conception by

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twin. The authors were unable to predict whether a healthy fetus could result from a polar body twinning. However, a study in 2012 found that it is possible for a polar body to result in a healthy fetus.

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Li R, Montpetit A, Rousseau M, Wu SY, Greenwood CM, Spector TD, Pollak M, Polychronakos C, Richards JB (January 2014). "Somatic point mutations occurring early in development: a monozygotic twin study".

1192:. Premature birth and low birth weights, especially when under 3.5 pounds (1.6 kg), can increase the risk of several health-related issues, such as vision and hearing loss, mental disabilities, and 428:

however, because even within the confines of the womb, the fetuses touch different parts of their environment, giving rise to small variations in their corresponding prints and thus making them unique.

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automatically implies dizygotic twins, but if monozygotic twins separate early enough, the arrangement of sacs and placentas in utero is in fact indistinguishable from that of dizygotic twins.

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Unlike singleton gestation where identification of patients at risk for PTL is often difficult, every multiple gestation is at risk for PTL, so all patients can be managed as being at risk.

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influence. Twins that have been separated early in life and raised in separate households are especially sought-after for these studies, which have been used widely in the exploration of

1125:, mystifyingly, was not the mother of two of her three children; she was found to be a chimera, and the two children were conceived from eggs derived from cells of their mother's twin. 1214:

Twin-to-twin transfusion syndrome (TTTS) illustration of twins showing one fetus with exposure to more amniotic fluid while the other is "stuck" with the membrane tightly around itself

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around 4–5) to 15 and more per thousand in some parts of India and up to over 20 in some Central African countries. The exact cause for the splitting of a zygote or embryo is unknown.

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arise from sesquizygotic (semi-identical) twinning which happens when a single egg is fertilized by two sperm and splits the three sets of chromosomes into two separate cell sets.

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Monozygotic twins, although genetically very similar, are not genetically exactly the same. The DNA in white blood cells of 66 pairs of monozygotic twins was analyzed for 506,786

3805: 1934: 1322:. One 1992 study estimates that the frequency of heteropaternal superfecundation among dizygotic twins, whose parents were involved in paternity suits, was approximately 2.4%. 613:(called Monochorionic-Diamniotic "MoDi"), which occurs in 60–70% of the pregnancies with monozygotic twins, and in 0.3% of all pregnancies. Monochorionic-Diamniotic twins are 3720: 4244: 3690: 3247: 498:

showed that although its fetal development suggested that it was an identical twin, as it shared a placenta with its healthy twin, tests revealed that it was probably a

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O. Bomsel-Helmreich; W. Al Mufti (1995). "The mechanism of monozygosity and double ovulation". In Louis G. Keith; Emile Papierik; Donald M. Keith; Barbara Luke (eds.).

165:, the lowest rates are found; only 6 to 9 twin sets per 1,000 live births. North America and Europe have intermediate rates of 9 to 16 twin sets per 1,000 live births. 1369:(45,X). In these cases, although the twins did form from the same fertilized egg, it is incorrect to refer to them as genetically identical, since they have different 2069: 800: 315:. Dizygotic twinning ranges from six per thousand births in Japan (similar to the rate of monozygotic twins) to 14 and more per thousand in some African countries. 137:

have the highest rate of twinning in the world, at 45–50 twin sets (90–100 twins) per 1,000 live births, possibly because of high consumption of a specific type of

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Schmid, O; Trautmann, U; Ashour, H; Ulmer, R; Pfeiffer, RA; Beinder, E (Dec 2000). "Prenatal diagnosis of heterokaryotypic mosaic twins discordant for fetal sex".

3776: 256:(also referred to as "non-identical twins", "dissimilar twins", "biovular twins", and, informally in the case of females, "sororal twins") usually occur when two 4911: 4562: 5180:

Girela, Eloy; Lorente, Jose A.; Alvarez, J. Carlos; Rodrigo, Maria D.; Lorente, Miguel; et al. (1997). "Indisputable double paternity in dizygous twins".

3959: 3017: 1254:. Ectopic pregnancies must be resolved because they can be life-threatening to the mother. However, in most cases, the intrauterine pregnancy can be salvaged. 436:. Normally due to an environmental factor or the deactivation of different X chromosomes in female monozygotic twins, and in some extremely rare cases, due to 5100:

Nieuwint, Aggie; Van Zalen-Sprock, Rieteke; Hummel, Pieter; Pals, Gerard; Van Vugt, John; et al. (1999). "'Identical' twins with discordant karyotypes".

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Various types of chorionicity and amniosity (how the baby's sac looks) in monozygotic (one egg/identical) twins as a result of when the fertilized egg divides

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early in pregnancy, yet the pregnancy will continue; one twin was miscarried but the other was able to be carried to term. This occurrence is similar to the

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from various parts of the body. The number of cells derived from each fetus can vary from one part of the body to another, and often leads to characteristic

841:. In Cândido Godói, one in five pregnancies has resulted in twins. The Argentine historian Jorge Camarasa has put forward the theory that experiments of the 1011:

level of experience of the obstetrician, the wish of the women giving birth, or the "management strategies" of the procedure of delivering the second twin.

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The widespread use of fertility drugs causing hyperovulation (stimulated release of multiple eggs by the mother) has caused what some call an "epidemic of

4094:; (3) when either of the twins had died in the womb before the onset of labor; and (4) when the pregnancy had been complicated by fetal malformations or 4047:

Stein W, Misselwitz B, Schmidt S (2008). "Twin-to-twin delivery time interval: influencing factors and effect on short-term outcome of the second twin".

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towards the other. Sometimes the parasitic twin becomes an almost indistinguishable part of the other, and sometimes this needs to be treated medically.

299:. Dizygotic twins share on average 50 percent of each other's genes, the same as siblings that are conceived and born at different times. Like any other 787:

and procedures such as IVF, which result in multiple births more frequently than unassisted fertilizations do. It may also be linked to the increase of

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From 1980 to 1997, the number of twin births in the United States rose 52%. This rise can at least partly be attributed to the increasing popularity of

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Matte, U; Le Roux, MG; Bénichou, B; Moisan, JP; Giugliani, R (1996). "Study on possible increase in twinning rate at a small village in south Brazil".

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is an exceedingly rare type of dizygotic twinning in which one twin implants in the uterus as normal and the other remains in the fallopian tube as an

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The human twin birth rate in the United States rose 76% from 1980 through 2009, from 9.4 to 16.7 twin sets (18.8 to 33.3 twins) per 1,000 births. The

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Guinness World Record holding twins: https://www.guinnessworldrecords.com/news/2022/11/theyre-so-different-even-though-theyre-identical-twins-725135

3747: 2128: 1880: 307:, particularly as they are the same age. However, dizygotic twins may also look very different from each other (for example, be of opposite sexes). 3827: 3091:

Scott, Richard T.; Treff, Nathan R.; Stevens, John; Forman, Eric J.; Hong, Kathleen H.; Katz-Jaffe, Mandy G.; Schoolcraft, William B. (June 2012).

2560:"Time-lapse recordings reveal why IVF embryos are more likely to develop into twins. Researchers believe the laboratory culture could be the cause" 5482: 1760: 1432:

male. The exact mechanism of fertilization could not be determined but the study stated that it was unlikely to be a case of polar body twinning.

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who happen to develop in the womb together and who are born at the same time, since they arise from two separate eggs fertilized by two separate

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Orwant, Jon. "Heterogeneous learning in the Doppelgänger user modeling system." User Modeling and User-Adapted Interaction 4.2 (1994): 107-130.

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contains two inner cell masses (ICM), each of which will lead to a separate fetus, rather than by the embryo splitting while hatching from the

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and the cell divides into two, with each daughter cell now containing the correct number of chromosomes. The cells continue to develop into a

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Comparison of zygote development in monozygotic and dizygotic twins. In the uterus, a majority of monozygotic twins (60–70%) share the same

4337: 1726: 5096:(Palgrave Macmillan; 2010) 221 pages; explores the experience of child twins, adult twins, and parents of twins, with a focus on Britain. 4976: 3492: 1401:. If the morula then undergoes a twinning event, two embryos will be formed, with different paternal genes but identical maternal genes. 4141:

Gedda, Luigi (1995). "The role of research in twin medicine". In Louis G. Keith; Emile Papiernik; Donald M. Keith; Barbara Luke (eds.).

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is recommended at between 37 and 38 weeks. Vaginal delivery in this case does not worsen the outcome for the infant as compared with

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Sometimes one twin fetus will fail to develop completely and continue to cause problems for its surviving twin. One fetus acts as a

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DiDi twins have the lowest mortality risk at about 9 percent, although that is still significantly higher than that of singletons.

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IVF techniques are more likely to create dizygotic twins. For IVF deliveries, there are nearly 21 pairs of twins for every 1,000.

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monozygotic twinning, a 2007 theory related to in vitro fertilization (IVF) proposes that monozygotic twins may be formed when a

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R. Derom; J. Orlebeke; A. Eriksson; M. Thiery (1995). "The epidemiology of multiple births in Europe". In Louis G. Keith (ed.).

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Biswas, A; Su, LL; Mattar, C (Apr 2013). "Caesarean section for preterm birth and, breech presentation and twin pregnancies".

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Female-male twins: This is the most common pairing (50%), encompassing both "female-male" (25%) and "male-female" (25%) twins.

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Martin, Joyce A.; Hamilton, Brady E.; Osterman, Michelle J.K. "Three Decades of Twin Births in the United States, 1980–2009"

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syndrome. Also, in an unknown proportion of cases, two zygotes may fuse soon after fertilization, resulting in a single

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yielded a mean delivery time interval of 13.5 minutes. The delivery interval between the twins was measured as follows:

4431: 5476: 4664: 2559: 2348:

Bortolus, Renata; Fabio Parazzini; Liliane Chatenoud; Guido Benzi; Massimiliano Maria Bianchi; Alberto Marini (1999).

291:

Dizygotic twins, like any other siblings, will practically always have different sequences on each chromosome, due to

5558: 5479:, who are twins and joined the Army on a same day, were promoted to the rank of Major General, again on the same day. 4552: 4095: 4006:

Kulkarni, A. D.; Jamieson, D. J.; Jones, H. W. Jr.; Kissin, D. M.; Gallo, M. F.; MacAluso, M.; Adashi, E. Y. (2013).

3931: 3232: 2880: 1557: 1205: 666: 629: 304: 17: 5220: 4447:"Prospective risk of stillbirth and neonatal complications in twin pregnancies: systematic review and meta-analysis" 3009: 1305:. Classical twin studies are now being supplemented with molecular genetic studies which identify individual genes. 260:

eggs are implanted in the uterus wall at the same time. When two eggs are independently fertilized by two different

5653: 5563: 2269: 952: 1605:

increased output of twins during periods of evolutionary distress and natural selection. Through their studies on

41: 4265: 2808:

Fraga, Mario F.; Ballestar, Esteban; Paz, Maria F.; Ropero, Santiago; Setien, Fernando; et al. (July 2005).

1843: 452: 5507: 2686:

Machin, GA (January 1996). "Some causes of genotypic and phenotypic discordance in monozygotic twin pairs".

771:

present in dairy products may increase the chance of dizygotic twinning. Specifically, the study found that

4880: 3150:"Postzygotic diploidization of triploids as a source of unusual cases of mosaicism, chimerism and twinning" 1693: 746: 3743: 2120: 1872: 1584:

responsible for the likelihood of twins, rather than the likelihood of litters (Whitcomb, 2021). Cases of

1196:. There is an increased possibility of potential complications as the birth weight of the baby decreases. 376:

Monozygotic twins may also be created artificially by embryo splitting. It can be used as an expansion of

2244: 2209: 925:

Dizygotic twin pregnancies are slightly more likely when the following factors are present in the woman:

4445:

Cheong-See F, Schuit E, Arroyo-Manzano D, Khalil A, Barrett J, Joseph KS, et al. (September 2016).

3929: 3835: 4335: 1756: 780:

is given to cattle, appear to enhance the chances of multiple pregnancies due to ovarian stimulation."

768: 537: 3513: 2518: 4993: 2419: 1160:, resulting in little or no fetus and a cancerous, overgrown placenta, resembling a bunch of grapes. 1036: 742: 695:

Mortality is highest for conjoined twins due to the many complications resulting from shared organs.

5194: 4767: 3403: 3391: 5500: 1528: 1440: 4496:"Co-bedding in neonatal nursery for promoting growth and neurodevelopment in stable preterm twins" 2199: 353:. The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births. 5591: 5024: 3865: 3184: 1648: 1532: 392:

Monozygotic twinning occurs in birthing at a rate of about 3 in every 1000 deliveries worldwide.

50: 3093:"Delivery of a chromosomally normal child from an oocyte with reciprocal aneuploid polar bodies" 1723: 5415: 5189: 4973: 4348: 3489: 3332: 2397: 959: 958:

The risk of twin birth can vary depending on what types of fertility treatments are used. With

377: 35: 5074:

Hayashi, C (2007). "Relationship between Twin Language, Twins' Bond, and Social Competence".

4994:"What are mirror image twins? | Washington State Twin Registry | Washington State University" 4237:"Very Low Birthweight - Online Medical Encyclopedia - University of Rochester Medical Center" 2517:

Oleszczuk, Jaroslaw J.; Donald M. Keith; Louis G. Keith; William F. Rayburn (November 1999).

2299: 1247: 677:

Monoamniotic twins occur when the split takes place after the ninth day after fertilization.

468:

However, certain characteristics become more alike as twins age, such as IQ and personality.

292: 31: 3324: 5419: 5386: 5279: 4207: 3049: 2821: 2420:"Study: Time-lapse recordings reveal why IVF embryos are more likely to develop into twins" 1977: 1585: 1491: 1066: 784: 445: 2234: 986:

A 15-year German study of 8,220 vaginally delivered twins (that is, 4,110 pregnancies) in

726:

with the head pointing towards upper left. The twin at right in the image is shown in the

8: 5550: 3550: 1413: 1298: 598: 5283: 4639: 3233:"Semi-identical twins are rare, and doctors say they've identified the second case ever" 3053: 2957:

Gudmundur L. (2021-01-07). "Differences between germline genomes of monozygotic twins".

2825: 2516: 1981: 5622: 5568: 5378: 5366: 5302: 5267: 5248: 5168: 5125: 4853: 4609: 4584: 4528: 4495: 4471: 4446: 4399: 4374: 4146: 4072: 3930:

Fernand Leroy; Taiwo Olaleye-Oruene; Gesina Koeppen-Schomerus; Elizabeth Bryan (2002).

3912: 3900: 3671: 3280: 3200: 3125: 3092: 3065: 2990: 2844: 2809: 2790: 2746: 2663: 2638: 2614: 2589: 2239: 2204: 2000: 1965: 1698: 1643: 1589:

knowledge, this is the first report of monozygotic twinning in the dog confirmed using

1456: 1436: 1421: 1337: 1157: 1103: 1045: 838: 641: 5203: 3362: 3268: 5370: 5334: 5324: 5307: 5240: 5207: 5160: 5117: 5041: 5037: 4956: 4845: 4749: 4682: 4672: 4614: 4533: 4515: 4476: 4404: 4318: 4154: 4091: 4064: 4029: 3951: 3904: 3663: 3628: 3620: 3610: 3569: 3525: 3514:"Mechanisms of twinning: VII. Effect of diet and heredity on the human twinning rate" 3450: 3407: 3336: 3325: 3284: 3272: 3171: 3130: 3112: 3073: 3038: 2994: 2982: 2974: 2919: 2909: 2886: 2876: 2869: 2849: 2782: 2738: 2703: 2668: 2619: 2530: 2473: 2468: 2451: 2379: 2371: 2325: 2181: 2040: 2005: 1961: 1906: 1876: 1594: 1409: 1267: 1251: 837:

to 10% for Linha São Pedro, a tiny Brazilian settlement which belongs to the city of

507: 491: 5252: 5172: 5129: 4076: 3916: 3675: 3204: 2750: 1790: 589:

Dichorionic-Diamniotic twins form when splitting takes place by the third day after

5663: 5658: 5442: 5382: 5362: 5297: 5287: 5232: 5199: 5150: 5109: 5033: 4946: 4857: 4837: 4739: 4729: 4604: 4596: 4523: 4511: 4507: 4466: 4458: 4394: 4386: 4347:. Royal College of Obstetricians and Gynaecologist. pp. 70–103. Archived from 4310: 4056: 4019: 3943: 3896: 3655: 3470: 3440: 3264: 3192: 3161: 3120: 3104: 3057: 2966: 2839: 2829: 2794: 2774: 2730: 2695: 2658: 2650: 2609: 2601: 2463: 2361: 2347: 2173: 2032: 1995: 1985: 1683: 1606: 1572: 1344:, which exhibit differing ethnic and racial features. One such pairing was born in 1319: 1263: 1189: 962:(IVF), this is primarily due to the insertion of multiple embryos into the uterus. 873: 568: 91: 4314: 2778: 2605: 5578: 4980: 4390: 4336:

National Collaborating Centre for Women's and Children's Health (November 2011).

4150: 3727: 3496: 3477: 3387: 2937:

Mandler, G (2001). "Apart from genetics: What makes monozygotic twins similar?".

2091: 1990: 1796: 1730: 1658: 1366: 1262:

For otherwise healthy twin pregnancies where both twins are head down a trial of

1122: 1057: 700: 682: 533: 477: 381: 208:

is higher for twins, it leads to female twins being more common than male twins.

138: 5219:

Shinwell ES, Reichman B, Lerner-Geva L, Boyko V, Blickstein I (September 2007).

4904:"Doctors say they have identified rare set of semi-identical twins in Australia" 2164:

Nylander, Percy P. S. (July 1981). "The Factors That Influence Twinning Rates".

2023:

Elliott, JP (December 2008). "Preterm labor in twins and high-order multiples".

1633: 1459:

lethality, while the other two cell lines, each consisting of the same maternal

407: 192:

Male–male twins: Sometimes called fraternal (unrelated to zygosity) twins (25%).

122: 5617: 5586: 5272:

Proceedings of the National Academy of Sciences of the United States of America

4494:

Lai, Nai Ming; Foong, Siew Cheng; Foong, Wai Cheng; Tan, Kenneth (2016-04-14).

2970: 2492: 1673: 1539: 1479: 1193: 1173: 1134: 1041: 1029: 885: 788: 777: 754: 723: 670: 495: 370: 162: 150: 110: 5459:"Twin Zygosity Test for Dichorionic Diamniotic (Di/Di) Twins! Zygosity Reveal" 5155: 5138: 4951: 4934: 4841: 4798: 4375:"Trends in caesarean delivery for twin births in the United States: 1995-2008" 4060: 3659: 3108: 2177: 2036: 1811: 1210: 424:

same person), rather than first cousins. Identical twins do not have the same

5648: 5642: 5596: 5338: 4686: 4519: 4423: 3730: 3624: 3116: 2978: 2375: 2366: 2349: 1653: 1590: 1575:, because while litters are caused by the release of multiple eggs during an 1452: 1394: 934: 889: 877: 846: 834: 825:

About 1 in 90 human births (1.1%) results from a twin pregnancy. The rate of

818: 750: 727: 719: 692:

into 2 embryos occurs, 99% of the time it is within 8 days of fertilization.

590: 257: 154: 142: 134: 5292: 3632: 3429:"Monochorionic diamniotic infants without twin-to-twin transfusion syndrome" 3166: 3149: 3061: 2923: 2890: 2834: 5374: 5311: 5244: 5236: 5121: 5045: 4849: 4753: 4690: 4557: 4537: 4480: 4408: 4322: 4068: 4033: 3955: 3573: 3529: 3454: 3399: 3276: 3175: 3134: 2986: 2853: 2786: 2742: 2700:

10.1002/(SICI)1096-8628(19960122)61:3<216::AID-AJMG5>3.0.CO;2-S

2623: 2567: 2534: 2477: 2383: 2044: 2009: 1703: 1496: 1429: 1302: 1224: 1185: 900: 665:

Monoamniotic twins, as with diamniotic monochorionic twins, have a risk of

662:

The survival rate for monoamniotic twins is somewhere between 50% and 60%.

610: 576: 416: 261: 5211: 5164: 4960: 4734: 4717: 4024: 4007: 3947: 3908: 3769:"Seeing double: the village in deepest Kerala where twins have taken over" 3667: 3445: 3428: 3077: 2707: 2672: 2450:

Illmensee K, Levanduski M, Vidali A, Husami N, Goudas VT (February 2009).

2185: 234: 5627: 4718:"Molecular Support for Heterogonesis Resulting in Sesquizygotic Twinning" 4618: 3196: 2424: 1668: 1500: 1435:

The likely genetic basis of semi-identical twins was reported in 2019 by

1381: 1341: 1331: 1169: 967: 930: 892:, the twinning rate exceeded 3% of all births. Nevertheless, the rate of 656: 580: 464: 460: 425: 5114:

10.1002/(SICI)1097-0223(199901)19:1<72::AID-PD465>3.0.CO;2-V

4744: 4600: 2654: 1799:, National Center for Health Statistics Data Brief, No. 80, January 2012 1455:

to form three cell lines. The purely paternal cell line died out due to

1297:

characteristics to try to isolate genetic influence from epigenetic and

978:) has a relatively less but yet significant risk of multiple pregnancy. 4583:

Schmidt, R; EH Sobel; HM Nitowsky; H Dar; FH Allen Jr (February 1976).

3255: 3069: 2955: 2810:"Epigenetic differences arise during the lifetime of monozygotic twins" 2319: 1688: 1678: 1663: 1294: 1279: 1235: 618: 499: 437: 366: 158: 153:, there are 18–30 twin sets (or 36–60 twins) per 1,000 live births. In 118: 46: 4462: 3887:

Rehan N, Tafida DS (November 1980). "Multiple births in Hausa women".

3010:"Identical twins aren't always genetically identical, new study finds" 2519:"Projections of population-based twinning rates through the year 2100" 1062: 226: 1638: 1576: 1370: 1176:

syndrome, but typically occurs later, as the twin is not reabsorbed.

1153: 1110: 971: 830: 749:

of 15 weeks. There is no sign of any membrane between the fetuses. A

441: 288:, just like ordinary siblings. This is the most common type of twin. 170: 71: 67: 57: 5348:"Selection for Increased Brood Size in Historical Human Populations" 4444: 2735:

10.1002/1097-0223(200012)20:12<999::aid-pd948>3.0.co;2-e

1117:, composed of cells from a male twin and a female twin. In one case 757:

of parts of the upper thorax and head is shown of the twin at right.

5532: 4373:

Lee HC, Gould JB, Boscardin WJ, El-Sayed YY, Blumenfeld YJ (2011).

4303:

Best Practice & Research. Clinical Obstetrics & Gynaecology

4143:

Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome

2322:

Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome

2151:"Chinese Women Try to Bypass One-Child Policy With Pills for Twins" 1903:

Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome

1425: 1290: 1140: 1118: 1114: 1070: 854: 772: 625: 604: 544: 433: 412: 211: 5492: 5439:"Facts About Multiples: An Encyclopedia of Multiple Birth Records" 5099: 2452:"Human embryo twinning with applications in reproductive medicine" 1808: 4907: 3606: 3426: 1628: 1610: 1404: 1286: 908: 904: 863: 858: 813:

twin figures (early 20th-century) in the permanent collection of

699:

If the division of the zygote occurs later than the 12 days then

572: 472: 300: 296: 281: 5218: 2871:

Entwined lives: twins and what they tell us about human behavior

966:

without IVF has a very high risk of multiple birth. Reversal of

5022:

Thorpe, K (June 2006). "Twin children's language development".

4582: 4111:"I'll do it my way: twin is born three months after her sister" 4008:"Fertility Treatments and Multiple Births in the United States" 3427:

Cordero L, Franco A, Joy SD, O'Shaughnessy RW (December 2005).

2449: 2296:"Identical and Fraternal Twins – Determining Zygosity in Twins" 1581: 1464: 1398: 1361:

clinical determination that the multiples are not monozygotic.

1345: 1220: 867: 689: 647: 520: 350: 346: 269: 215: 102: 83: 79: 3691:"Nazi Angel of death Josef Mengel created twin town in Brazil" 3499:

By Pamela Prindle Fierro, About.com. Retrieved on July 9, 2009

1900: 1809:

Zach, Terence; Arun K Pramanik; Susannah P Ford (2007-10-02).

922:

The predisposing factors of monozygotic twinning are unknown.

722:

as part of IVF. The twin at left in the image is shown in the

5345: 5321:

Identical Strangers: A Memoir of Twins Separated and Reunited

1817: 1444: 1390: 1091: 1087: 1083: 1079: 987: 833:, ranging as high as about 45 per 1000 births (4.5%) for the 810: 285: 146: 121:

whose resemblance parallels that of twins are referred to as

98: 2400:. MedlinePlus, US National Library of Medicine. 11 July 2022 2398:"Is the probability of having twins determined by genetics?" 1597:

and geographical population diffusion of armadillo species.

1451:

simultaneously. The chromosomes assorted themselves through

1227:. The lives of both twins are endangered by this condition. 471:

In January 2021, new research from a team of researchers in

349:(hence, "monozygotic") which then divides into two separate 5179: 4005: 1448: 1386: 842: 373:(the gelatinous protective coating around the blastocyst). 342: 312: 54: 3645: 3394:. In Robert Resnik; Robert K. Creasy; Jay D. Iams (eds.). 2720: 1927:"What's in a yam? Clues to fertility, a student discovers" 189:

Female–female twins: Sometimes called sororal twins (25%).

4768:"Rare new kind of twins: boy and girl are semi-identical" 4372: 1460: 801:

Populated places with highest incidence of multiple birth

718:

Dichorionic-diamniotic twins at 8 weeks and 5 days since

459:

Another cause of difference between monozygotic twins is

5268:"Male twins reduce fitness of female co-twins in humans" 5136: 4826: 3721:

Nazi 'Angel of Death' not responsible for town of twins

3090: 2807: 1376: 1351: 1073:) in 1811, were the origin of the term "Siamese twins". 4046: 2166:

Acta Geneticae Medicae et Gemellologiae: Twin Research

1959: 821:

have the highest dizygotic twinning rate in the world.

485: 380:(IVF) to increase the number of available embryos for 5318: 4728:(9). Boston: Massachusetts Medical Society: 842–849. 4716:

Gabbett, Michael T.; et al. (28 February 2019).

3548: 2763: 2564:

European Society of Human Reproduction and Embryology

4873:"Study describes new type of "semi-identical" twins" 1199: 1113:

skin coloration in human chimeras. A chimera may be

914:

Twins are more common in people of African descent.

402: 5475:Twin brothers promoted as Majors General together. 5265: 27:

One of two offspring produced by the same pregnancy

5346:Helle, Samuli; Virpi Lummaa; Jukka Jokela (2004). 5139:"How frequent is heteropaternal superfecundation?" 5094:Twins in Society: Parents, Bodies, Space, and Talk 4933:Gedda L, Sciacca A, Brenci G, et al. (1984). 4932: 4175: 4109: 2868: 1810: 896:twins remains at about 1 in 333 across the globe. 105:(the much more common case in humans) is called a 78:('identical'), meaning that they develop from one 4983:. Proactivegenetics.com. Retrieved on 2013-08-10. 3466: 3464: 2298:. Multiples.about.com. 2013-07-16. Archived from 1746:in "Human Heredity Principles and issues" p. 104. 1018: 280:. Fraternal twins are, essentially, two ordinary 5640: 5137:Wenk RE, Houtz T, Brooks M, Chiafari FA (1992). 4974:Twins genetics, details of environmental impacts 4935:"Situs viscerum specularis in monozygotic twins" 4493: 3932:"Yoruba Customs and Beliefs Pertaining to Twins" 3858:"Mohammadpur Umri, THE VILLAGE OF TWINS !!" 3396:Maternal-Fetal Medicine: Principles and Practice 3331:. Washington, DC: Taylor & Francis. p. 2272:. Washington State Twin Registry. October 2015. 1348:in 1993 to a white mother and Caribbean father. 1223:, the other, the 'recipient' twin, is large and 1184:It is very common for twins to be born at a low 322: 4421: 3549:Martin, Joyce A; Melissa M. Park (1999-09-14). 3322: 2636: 1757:"Twins, Triplets, Multiple Births: MedlinePlus" 567:Normally, twins have two separate (di- being a 4300: 4266:"Pregnant with twins: potential complications" 3600: 3461: 3182: 3007: 2490: 1490:There have been many studies highlighting the 1463:but only 50% identical paternal DNA, formed a 221: 109:, and the general term for one offspring of a 5508: 5266:Lummaa V, Pettay JE, Russell AF (June 2007). 3356: 3354: 3352: 3097:Journal of Assisted Reproduction and Genetics 943:She is greater than average height and weight 617:monozygotic, with a few exceptions where the 185:Fraternal twins can be any of the following: 4438: 4366: 4329: 3551:"Trends in Twin and Triplet Births: 1980–97" 3490:MoMo Twins; Monochorionic Monoamniotic Twins 2757: 2590:"Mechanical control of tissue morphogenesis" 2270:"Are there more male twins or female twins?" 899:In a study on the maternity records of 5750 5059:Usher, L (13 October 2000). "Idioglossia". 4500:The Cochrane Database of Systematic Reviews 3886: 3864:. Business Directory Plugin. Archived from 3603:Progress in Reproductive Medicine Volume II 2484: 2343: 2341: 1318:This phenomenon is known as heteropaternal 888:". In 2001, for the first time ever in the 506:In 2003, a study argued that many cases of 264:, fraternal twins result. The two eggs, or 5515: 5501: 4796: 4296: 4294: 4292: 4290: 3688: 3386: 3349: 3318: 3316: 3314: 3312: 3310: 3308: 3147: 2714: 2587: 1717: 5301: 5291: 5193: 5154: 4950: 4743: 4733: 4608: 4527: 4470: 4398: 4173: 4107: 4023: 3471:Pregnancy-Info -- > Monoamniotic Twins 3444: 3165: 3124: 2843: 2833: 2662: 2613: 2467: 2365: 2062:"Probability of having twins hereditary?" 1999: 1989: 1558:Learn how and when to remove this message 1542:so that sources are clearly identifiable. 946:She has had several previous pregnancies. 940:She is between the age of 30 and 40 years 650:in 1–2% of monozygotic twin pregnancies. 4671:. Sunderland, Mass: Sinauer Associates. 4550: 3987:. University of Rochester Medical Center 3511: 3507: 3505: 2637:Edwards JH, Dent T, Kahn J (June 1966). 2338: 2163: 1955: 1953: 1951: 1844:"Genetics or yams in the Land of Twins?" 1403: 1242: 1209: 1061: 804: 519: 406: 233: 225: 40: 5319:Schein, Elyse; Paula Bernstein (2007). 5143:Acta Geneticae Medicae et Gemellologiae 5073: 4879:. Thomson Reuters Trust. Archived from 4864: 4715: 4711: 4709: 4707: 4662: 4287: 4134: 3420: 3305: 2936: 2022: 1485: 917: 609:Monochorionic twins generally have two 513: 432:Monozygotic twins always have the same 238:Fraternal twin brothers as young babies 14: 5641: 5021: 4901: 4870: 4585:"Monozygotic twins discordant for sex" 3360: 2903: 2875:. New York: Dutton. pp. 135–138. 2685: 2127:. Associated Press. 14 February 2006. 1966:"Twinning across the Developing World" 1393:. The cell assorts the chromosomes by 1257: 1146: 543:It is a common misconception that two 5496: 5058: 4778:from the original on 28 February 2019 4774:. Thomson Reuters. 28 February 2019. 4174:Ainsworth, Chris (15 November 2003). 4140: 3880: 3601:Asch, Richard H.; John Studd (1995). 3566:National Center for Health Statistics 3502: 3483: 2866: 2350:"The epidemiology of multiple births" 2288: 2089: 1948: 1472: 1467:which subsequently split into twins. 1273: 903:women living in the Savannah zone of 815:The Children's Museum of Indianapolis 440:, twins may express different sexual 176: 169:genetically linked tendency to hyper- 149:to release an egg from each side. In 4704: 4422:James Gallagher (23 November 2011). 4040: 3594: 3245: 3211:from the original on 29 October 2021 3020:from the original on 11 January 2021 2688:American Journal of Medical Genetics 2639:"Monozygotic twins of different sex" 2523:The Journal of Reproductive Medicine 2262: 2131:from the original on 6 December 2008 1964:(2011). Newell, Marie-Louise (ed.). 1511: 1377:Semi-identical (sesquizygotic) twins 1352:Monozygotic twins of different sexes 1313: 1308: 1168:Occasionally, a woman will suffer a 981: 753:is shown of the twin at left, and a 688:When the division of the developing 5522: 4122:from the original on 30 August 2021 3808:from the original on 29 August 2018 3402:: W. B. Saunders Company. pp. 3185:"'Semi-identical' twins discovered" 2390: 2324:. Taylor and Francis. p. 145. 2121:"China: Drug bid to beat child ban" 1744:5-7 Twin Studies and Complex Traits 1733:Last Editorial Review: 19 June 2000 1724:MedicineNet > Definition of Twin 1499:was thought to be the major cause. 1179: 646:Monochorionic twins share the same 624:Monochorionic twins share the same 603:Monochorionic twins share the same 486:Polar body and semi-identical twins 24: 5456: 5436: 5367:10.1111/j.0014-3820.2004.tb01658.x 5086: 4902:Molina, Brett (28 February 2019). 4424:"Women can choose Caesarean birth" 4108:Crossland, David (16 April 2019). 3901:10.1111/j.1471-0528.1980.tb04464.x 3804:. Bennett, Coleman & Co. Ltd. 3148:Golubovsky, M.D. (February 2003). 1905:. Taylor and Francis. p. 34. 1163: 1128: 1051: 1023: 730:with the head pointing rightwards. 25: 5675: 5559:Twin-to-twin transfusion syndrome 5488: 4665:"Non-identical Monozygotic Twins" 4188:from the original on 20 June 2015 4096:Twin-to-twin transfusion syndrome 3558:National Vital Statistics Reports 2276:from the original on 24 July 2018 1206:Twin-to-twin transfusion syndrome 1200:Twin-to-twin transfusion syndrome 1152:results when one twin has either 667:twin-to-twin transfusion syndrome 630:twin-to-twin transfusion syndrome 532:In very rare cases, twins become 403:Genetic and epigenetic similarity 214:is the degree of identity in the 5564:Twin reversed arterial perfusion 5076:Twin Research and Human Genetics 5038:10.1016/j.earlhumdev.2006.03.012 4434:from the original on 2012-08-19. 4090:the first twin was delivered by 3981:"Overview of Multiple Pregnancy" 3701:from the original on 19 May 2019 3365:. Focus Information Technology. 3323:Shulman LS, van Vugt JG (2006). 3183:John Whitfield (26 March 2007). 2588:Patwari P, Lee RT (2008-08-01). 2469:10.1016/j.fertnstert.2008.12.098 2090:Fitch, Karen (26 January 2005). 1540:add missing citation information 1516: 1447:from the same man fertilized an 953:assisted reproductive technology 735: 711: 200:susceptible than females to die 5405:"TWINS Guide to the First Year" 5067: 5052: 5015: 5004:from the original on 2018-09-05 4986: 4967: 4926: 4895: 4820: 4809:from the original on 2023-04-29 4790: 4760: 4722:New England Journal of Medicine 4656: 4625: 4576: 4565:from the original on 2018-01-19 4551:Moorhead, Joanna (2011-09-24). 4544: 4487: 4415: 4276:from the original on 2015-11-09 4258: 4247:from the original on 2018-01-19 4229: 4218:from the original on 2019-04-05 4208:"Risks Linked With Twin Births" 4200: 4167: 4101: 4083: 4012:New England Journal of Medicine 3999: 3973: 3969:– via Randafricanart.com. 3962:from the original on 2017-09-02 3923: 3850: 3820: 3790: 3761: 3750:from the original on 2009-07-18 3746:. BBC World News. 7 June 2001. 3736: 3713: 3682: 3639: 3583:from the original on 2017-11-13 3542: 3380: 3369:from the original on 2008-06-16 3239: 3225: 3141: 3084: 3032: 3001: 2949: 2930: 2897: 2860: 2801: 2679: 2630: 2581: 2552: 2541:from the original on 2009-01-04 2510: 2499:from the original on 2022-02-07 2443: 2432:from the original on 2019-08-05 2412: 2313: 2251:from the original on 2021-07-01 2227: 2216:from the original on 2021-12-12 2192: 2157: 2143: 2113: 2102:from the original on 2022-06-24 2083: 2072:from the original on 2022-09-25 2054: 2016: 1937:from the original on 2022-05-07 1919: 1883:from the original on 2008-12-15 1854:from the original on 2017-02-23 1825:from the original on 2008-09-25 1763:from the original on 2016-06-03 762: 453:single-nucleotide polymorphisms 92:heteropaternal superfecundation 4998:Washington State Twin Registry 4939:Acta Genet Med Gemellol (Roma) 4871:Dunham, Will (26 March 2007). 4512:10.1002/14651858.CD008313.pub3 3834:. 4Skylark.com. Archived from 3689:Nick Evans (21 January 2009). 3648:Acta Genet Med Gemellol (Roma) 1894: 1865: 1836: 1802: 1783: 1774: 1749: 1736: 1357:accepted as a sound basis for 1325: 1230: 1019:Complications during pregnancy 829:twinning varies greatly among 13: 1: 5204:10.1016/S0015-0282(97)81456-2 4315:10.1016/j.bpobgyn.2012.09.002 3775:. 12 May 2009. Archived from 3269:10.1016/s0140-6736(03)14237-7 3008:Lianne Kolirin (8 Jan 2021). 2779:10.1136/jmedgenet-2013-101712 2606:10.1161/CIRCRESAHA.108.175331 2491:April Holladay (2001-05-09). 1710: 475:was published in the journal 323:Monozygotic (identical) twins 128: 82:, which splits and forms two 4391:10.1097/AOG.0b013e3182318651 2939:Journal of Mind and Behavior 2814:Proc. Natl. Acad. Sci. U.S.A 2566:. 2007-07-02. Archived from 1991:10.1371/journal.pone.0025239 1694:Twin towns and sister cities 1097: 794: 767:A 2006 study has found that 387: 356: 7: 4910:. USA TODAY. Archived from 4797:NEJM Group (4 March 2019). 4589:Journal of Medical Genetics 3828:"Twin Capital Of The World" 3512:Steinman, Gary (May 2006). 3361:Curran, Mark (2005-11-02). 2643:Journal of Medical Genetics 2245:Central Intelligence Agency 2210:Central Intelligence Agency 2153:. ABC News. August 3, 2011. 1621: 1048:embryo, and, later, fetus. 745:of monoamniotic twins at a 490:A 1981 study of a deceased 448:zygote splitting unevenly. 222:Dizygotic (fraternal) twins 204:, and since the death rate 101:that develops alone in the 10: 5680: 5323:. New York: Random House. 4663:Gilbert, Scott F. (2006). 2971:10.1038/s41588-020-00755-1 1507: 1329: 1277: 1203: 1132: 1101: 1055: 1027: 798: 769:insulin-like growth factor 642:Monochorionic-Monoamniotic 628:, and thus have a risk of 345:is fertilized to form one 29: 5610: 5577: 5549: 5531: 5156:10.1017/S000156600000249X 5061:Times Literary Supplement 4952:10.1017/S0001566000007546 4842:10.1007/s00439-006-0279-x 4061:10.1080/00016340801934276 4049:Acta Obstet Gynecol Scand 3660:10.1017/S0001566000000829 3480:Retrieved on July 9, 2009 3109:10.1007/s10815-012-9746-6 2493:"What triggers twinning?" 2354:Human Reproduction Update 2178:10.1017/s0001566000007650 2037:10.1016/j.clp.2007.10.004 1340:couples can sometimes be 1121:determined that a woman, 1037:obstetric ultrasonography 850:of the world, including: 743:Abdominal ultrasonography 361:Regarding spontaneous or 4799:"Sesquizygotic Twinning" 2908:. New York: Worth Pubs. 2867:Segal, Nancy L. (1999). 2098:. The Tech Interactive. 994:Within 15 minutes: 75.8% 964:Ovarian hyperstimulation 703:are usually the result. 599:Monochorionic-Diamniotic 145:which may stimulate the 5654:Reproduction in mammals 5592:Craniopagus parasiticus 5293:10.1073/pnas.0605875104 5182:Fertility and Sterility 5025:Early Human Development 4553:"Black and white twins" 3733:online, 27 January 2009 3062:10.1126/science.7196086 2904:Plomin, Robert (2001). 2835:10.1073/pnas.0500398102 2200:"United States: People" 2068:. Columbia University. 2025:Clinics in Perinatology 1649:List of multiple births 1492:development of language 974:(trade names including 673:due to lack of oxygen. 652:Monoamniotic twins are 564:Dichorionic-Diamniotic 538:pregnancy complications 461:epigenetic modification 444:, normally from an XXY 5418:. 2008. Archived from 5416:Fort Collins, Colorado 5237:10.1542/peds.2006-3574 4241:www.urmc.rochester.edu 2367:10.1093/humupd/5.2.179 1931:Yale Medicine Magazine 1416: 1215: 1074: 960:in vitro fertilisation 822: 525: 420: 378:in vitro fertilization 239: 231: 74:. Twins can be either 60: 36:Twins (disambiguation) 4735:10.1056/NEJMoa1701313 4669:Developmental biology 4633:"The Zygosity Puzzle" 4177:"The stranger within" 4025:10.1056/NEJMoa1301467 3948:10.1375/1369052023009 3446:10.1038/sj.jp.7211405 3167:10.1093/humrep/deg060 1742:Michael R. Cummings, 1654:List of notable twins 1407: 1389:is fertilized by two 1336:Dizygotic twins from 1248:Heterotopic pregnancy 1243:Heterotopic pregnancy 1213: 1156:or complete paternal 1065: 1006:Over 60 minutes: 1.8% 808: 523: 410: 293:chromosomal crossover 237: 230:Adult fraternal twins 229: 141:containing a natural 70:produced by the same 44: 32:Twin (disambiguation) 5477:Seneviratne brothers 3889:Br J Obstet Gynaecol 3798:"A village of twins" 3392:"Multiple Gestation" 3197:10.1038/news070326-1 2594:Circulation Research 1586:monozygotic twinning 1527:needs more complete 1486:Language development 1069:, born in Siam (now 1067:Chang and Eng Bunker 997:16–30 minutes: 16.4% 933:descent (especially 918:Predisposing factors 514:Degree of separation 446:Klinefelter syndrome 341:occur when a single 30:For other uses, see 5551:Monochorionic twins 5284:2007PNAS..10410915L 4914:on 28 February 2019 4883:on 28 February 2019 4601:10.1136/jmg.13.1.64 4338:"Caesarean section" 3985:Health Encyclopedia 3744:"The Land Of Twins" 3054:1981Sci...213..775B 2906:Behavioral genetics 2826:2005PNAS..10210604F 2655:10.1136/jmg.3.2.117 1982:2011PLoSO...625239S 1873:"The Land of Twins" 1414:Miles City, Montana 1408:Twin calves of the 1258:Management of birth 1147:Partial molar twins 1003:46–60 minutes: 1.7% 1000:31–45 minutes: 4.3% 583:(identical) twins. 5569:Monoamniotic twins 5437:Samson, Jennifer. 5102:Prenatal Diagnosis 4979:2021-08-31 at the 4147:Taylor and Francis 3726:2014-10-25 at the 3495:2016-04-08 at the 3476:2019-11-03 at the 3154:Human Reproduction 2240:The World Factbook 2205:The World Factbook 1848:Independent Online 1795:2017-12-18 at the 1729:2013-10-22 at the 1699:Twins in mythology 1644:Gemini (astrology) 1473:Mirror image twins 1457:genomic imprinting 1417: 1274:Human twin studies 1216: 1158:uniparental disomy 1104:Chimera (genetics) 1075: 823: 526: 421: 415:but have separate 303:, dizygotic twins 272:, hence the terms 240: 232: 177:Types and zygosity 61: 5636: 5635: 5330:978-1-4000-6496-0 4678:978-0-87893-250-4 4463:10.1136/bmj.i4353 4160:978-1-85070-666-3 4092:caesarean section 4018:(23): 2218–2225. 3838:on 4 October 2015 3616:978-1-85070-574-1 3413:978-0-7216-0004-8 3342:978-0-8247-2844-1 3327:Prenatal medicine 3048:(4509): 775–777. 2915:978-0-7167-5159-5 2562:(Press release). 2331:978-1-85070-666-3 1962:Christiaan Monden 1912:978-1-85070-666-3 1877:BBC World Service 1812:"Multiple Births" 1595:genetic variation 1568: 1567: 1560: 1314:Bi-paternal twins 1309:Unusual twinnings 1268:Caesarean section 1252:ectopic pregnancy 982:Delivery interval 809:A pair of female 707: 706: 18:Monozygotic twins 16:(Redirected from 5671: 5517: 5510: 5503: 5494: 5493: 5468: 5466: 5465: 5453: 5451: 5450: 5441:. Archived from 5433: 5431: 5430: 5424: 5409: 5400: 5398: 5397: 5391: 5385:. Archived from 5352: 5342: 5315: 5305: 5295: 5278:(26): 10915–20. 5262: 5260: 5259: 5215: 5197: 5176: 5158: 5133: 5080: 5079: 5071: 5065: 5064: 5056: 5050: 5049: 5019: 5013: 5012: 5010: 5009: 4990: 4984: 4971: 4965: 4964: 4954: 4930: 4924: 4923: 4921: 4919: 4899: 4893: 4892: 4890: 4888: 4868: 4862: 4861: 4824: 4818: 4817: 4815: 4814: 4794: 4788: 4787: 4785: 4783: 4764: 4758: 4757: 4747: 4737: 4713: 4702: 4701: 4699: 4698: 4689:. Archived from 4660: 4654: 4653: 4651: 4650: 4644: 4638:. 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Archived from 3263:(9385): 735–43. 3252: 3246:Hall JG (2003). 3243: 3237: 3236: 3229: 3223: 3220: 3218: 3216: 3179: 3169: 3145: 3139: 3138: 3128: 3088: 3082: 3081: 3036: 3030: 3029: 3027: 3025: 3005: 2999: 2998: 2953: 2947: 2946: 2934: 2928: 2927: 2901: 2895: 2894: 2874: 2864: 2858: 2857: 2847: 2837: 2805: 2799: 2798: 2761: 2755: 2754: 2729:(12): 999–1003. 2718: 2712: 2711: 2683: 2677: 2676: 2666: 2634: 2628: 2627: 2617: 2585: 2579: 2578: 2576: 2575: 2556: 2550: 2549: 2547: 2546: 2514: 2508: 2507: 2505: 2504: 2488: 2482: 2481: 2471: 2447: 2441: 2440: 2438: 2437: 2416: 2410: 2409: 2407: 2405: 2394: 2388: 2387: 2369: 2345: 2336: 2335: 2317: 2311: 2310: 2308: 2307: 2292: 2286: 2285: 2283: 2281: 2266: 2260: 2259: 2257: 2256: 2231: 2225: 2224: 2222: 2221: 2196: 2190: 2189: 2161: 2155: 2154: 2147: 2141: 2140: 2138: 2136: 2117: 2111: 2110: 2108: 2107: 2096:Ask a Geneticist 2087: 2081: 2080: 2078: 2077: 2058: 2052: 2051: 2020: 2014: 2013: 2003: 1993: 1957: 1946: 1945: 1943: 1942: 1923: 1917: 1916: 1898: 1892: 1891: 1889: 1888: 1869: 1863: 1862: 1860: 1859: 1840: 1834: 1833: 1831: 1830: 1814: 1806: 1800: 1787: 1781: 1778: 1772: 1771: 1769: 1768: 1753: 1747: 1740: 1734: 1721: 1684:Superfecundation 1607:Vespertilionidae 1563: 1556: 1552: 1549: 1543: 1520: 1519: 1512: 1320:superfecundation 1264:vaginal delivery 1180:Low birth weight 874:Mohammadpur Umri 739: 715: 569:numerical prefix 550: 549: 305:may look similar 45:Identical twins 21: 5679: 5678: 5674: 5673: 5672: 5670: 5669: 5668: 5639: 5638: 5637: 5632: 5606: 5579:Conjoined twins 5573: 5545: 5527: 5521: 5491: 5463: 5461: 5448: 5446: 5428: 5426: 5422: 5407: 5403: 5395: 5393: 5389: 5350: 5331: 5257: 5255: 5195:10.1.1.378.4082 5089: 5087:Further reading 5084: 5083: 5072: 5068: 5057: 5053: 5020: 5016: 5007: 5005: 4992: 4991: 4987: 4981:Wayback Machine 4972: 4968: 4931: 4927: 4917: 4915: 4900: 4896: 4886: 4884: 4869: 4865: 4825: 4821: 4812: 4810: 4795: 4791: 4781: 4779: 4766: 4765: 4761: 4714: 4705: 4696: 4694: 4679: 4661: 4657: 4648: 4646: 4642: 4635: 4631: 4630: 4626: 4581: 4577: 4568: 4566: 4549: 4545: 4506:(2): CD008313. 4492: 4488: 4443: 4439: 4420: 4416: 4385:(5): 1095–101. 4371: 4367: 4357: 4355: 4351: 4340: 4334: 4330: 4299: 4288: 4279: 4277: 4264: 4263: 4259: 4250: 4248: 4235: 4234: 4230: 4221: 4219: 4206: 4205: 4201: 4191: 4189: 4172: 4168: 4161: 4139: 4135: 4125: 4123: 4106: 4102: 4088: 4084: 4045: 4041: 4004: 4000: 3990: 3988: 3979: 3978: 3974: 3965: 3963: 3928: 3924: 3885: 3881: 3871: 3869: 3862:himsamachar.com 3856: 3855: 3851: 3841: 3839: 3826: 3825: 3821: 3811: 3809: 3796: 3795: 3791: 3782: 3780: 3773:The Independent 3767: 3766: 3762: 3753: 3751: 3742: 3741: 3737: 3728:Wayback Machine 3718: 3714: 3704: 3702: 3687: 3683: 3644: 3640: 3617: 3599: 3595: 3586: 3584: 3580: 3553: 3547: 3543: 3534: 3532: 3510: 3503: 3497:Wayback Machine 3488: 3484: 3478:Wayback Machine 3469: 3462: 3425: 3421: 3414: 3385: 3381: 3372: 3370: 3359: 3350: 3343: 3321: 3306: 3297: 3295: 3291: 3250: 3244: 3240: 3231: 3230: 3226: 3214: 3212: 3146: 3142: 3089: 3085: 3037: 3033: 3023: 3021: 3006: 3002: 2959:Nature Genetics 2954: 2950: 2935: 2931: 2916: 2902: 2898: 2883: 2865: 2861: 2820:(30): 10604–9. 2806: 2802: 2762: 2758: 2719: 2715: 2684: 2680: 2635: 2631: 2586: 2582: 2573: 2571: 2558: 2557: 2553: 2544: 2542: 2529:(11): 913–921. 2515: 2511: 2502: 2500: 2495:. WonderQuest. 2489: 2485: 2448: 2444: 2435: 2433: 2418: 2417: 2413: 2403: 2401: 2396: 2395: 2391: 2346: 2339: 2332: 2318: 2314: 2305: 2303: 2294: 2293: 2289: 2279: 2277: 2268: 2267: 2263: 2254: 2252: 2235:"Italy: People" 2233: 2232: 2228: 2219: 2217: 2198: 2197: 2193: 2162: 2158: 2149: 2148: 2144: 2134: 2132: 2119: 2118: 2114: 2105: 2103: 2088: 2084: 2075: 2073: 2060: 2059: 2055: 2021: 2017: 1960:Smits, Jeroen; 1958: 1949: 1940: 1938: 1925: 1924: 1920: 1913: 1899: 1895: 1886: 1884: 1871: 1870: 1866: 1857: 1855: 1842: 1841: 1837: 1828: 1826: 1807: 1803: 1797:Wayback Machine 1788: 1784: 1779: 1775: 1766: 1764: 1759:. 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Steril 2442: 2428:. 2007-07-02. 2411: 2389: 2360:(2): 179–187. 2337: 2330: 2312: 2287: 2261: 2247:. 2008-09-04. 2226: 2212:. 2008-09-04. 2191: 2172:(3): 189–202. 2156: 2142: 2112: 2082: 2053: 2031:(4): 599–609. 2015: 1947: 1918: 1911: 1893: 1879:. 2001-06-07. 1864: 1850:. 2007-11-12. 1835: 1801: 1782: 1773: 1748: 1735: 1715: 1714: 1712: 1709: 1707: 1706: 1701: 1696: 1691: 1686: 1681: 1676: 1674:Multiple birth 1671: 1666: 1661: 1656: 1651: 1646: 1641: 1636: 1631: 1625: 1623: 1620: 1566: 1565: 1524: 1522: 1515: 1509: 1506: 1487: 1484: 1480:situs inversus 1474: 1471: 1428:XX, and one a 1378: 1375: 1353: 1350: 1330:Main article: 1327: 1324: 1315: 1312: 1310: 1307: 1278:Main article: 1275: 1272: 1259: 1256: 1244: 1241: 1232: 1229: 1204:Main article: 1201: 1198: 1194:cerebral palsy 1181: 1178: 1174:vanishing twin 1165: 1162: 1148: 1145: 1135:Parasitic twin 1133:Main article: 1130: 1127: 1102:Main article: 1099: 1096: 1056:Main article: 1053: 1050: 1042:vanishing twin 1030:Vanishing twin 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5445:on 2009-10-15 5444: 5440: 5435: 5425:on 2008-10-30 5421: 5417: 5413: 5406: 5402: 5392:on 2008-10-02 5388: 5384: 5380: 5376: 5372: 5368: 5364: 5360: 5356: 5349: 5344: 5340: 5336: 5332: 5326: 5322: 5317: 5313: 5309: 5304: 5299: 5294: 5289: 5285: 5281: 5277: 5273: 5269: 5264: 5254: 5250: 5246: 5242: 5238: 5234: 5230: 5226: 5222: 5217: 5213: 5209: 5205: 5201: 5196: 5191: 5187: 5183: 5178: 5174: 5170: 5166: 5162: 5157: 5152: 5148: 5144: 5140: 5135: 5131: 5127: 5123: 5119: 5115: 5111: 5107: 5103: 5098: 5095: 5092:Bacon, Kate. 5091: 5090: 5077: 5070: 5062: 5055: 5047: 5043: 5039: 5035: 5031: 5027: 5026: 5018: 5003: 4999: 4995: 4989: 4982: 4978: 4975: 4970: 4962: 4958: 4953: 4948: 4944: 4940: 4936: 4929: 4913: 4909: 4905: 4898: 4882: 4878: 4874: 4867: 4859: 4855: 4851: 4847: 4843: 4839: 4836:(2): 179–85. 4835: 4831: 4823: 4808: 4804: 4800: 4793: 4777: 4773: 4769: 4763: 4755: 4751: 4746: 4741: 4736: 4731: 4727: 4723: 4719: 4712: 4710: 4708: 4693:on 2009-01-06 4692: 4688: 4684: 4680: 4674: 4670: 4666: 4659: 4645:on 2016-03-04 4641: 4634: 4628: 4620: 4616: 4611: 4606: 4602: 4598: 4594: 4590: 4586: 4579: 4564: 4560: 4559: 4554: 4547: 4539: 4535: 4530: 4525: 4521: 4517: 4513: 4509: 4505: 4501: 4497: 4490: 4482: 4478: 4473: 4468: 4464: 4460: 4456: 4452: 4448: 4441: 4433: 4429: 4425: 4418: 4410: 4406: 4401: 4396: 4392: 4388: 4384: 4380: 4376: 4369: 4354:on 2011-12-15 4350: 4346: 4339: 4332: 4324: 4320: 4316: 4312: 4309:(2): 209–19. 4308: 4304: 4297: 4295: 4293: 4291: 4275: 4271: 4267: 4261: 4246: 4242: 4238: 4232: 4217: 4213: 4209: 4203: 4187: 4183: 4182:New scientist 4178: 4170: 4162: 4156: 4152: 4148: 4144: 4137: 4121: 4117: 4112: 4104: 4097: 4093: 4086: 4078: 4074: 4070: 4066: 4062: 4058: 4055:(3): 346–53. 4054: 4050: 4043: 4035: 4031: 4026: 4021: 4017: 4013: 4009: 4002: 3986: 3982: 3976: 3961: 3957: 3953: 3949: 3945: 3941: 3937: 3936:Twin Research 3933: 3926: 3918: 3914: 3910: 3906: 3902: 3898: 3894: 3890: 3883: 3867: 3863: 3859: 3853: 3837: 3833: 3829: 3823: 3807: 3803: 3799: 3793: 3778: 3774: 3770: 3764: 3749: 3745: 3739: 3732: 3731:New Scientist 3729: 3725: 3722: 3716: 3700: 3696: 3695:The Telegraph 3692: 3685: 3677: 3673: 3669: 3665: 3661: 3657: 3653: 3649: 3642: 3634: 3630: 3626: 3622: 3618: 3612: 3608: 3604: 3597: 3579: 3575: 3571: 3567: 3563: 3559: 3552: 3545: 3531: 3527: 3523: 3519: 3515: 3508: 3506: 3498: 3494: 3491: 3486: 3479: 3475: 3472: 3467: 3465: 3456: 3452: 3447: 3442: 3439:(12): 753–8. 3438: 3434: 3430: 3423: 3415: 3409: 3405: 3401: 3397: 3393: 3389: 3383: 3368: 3364: 3357: 3355: 3353: 3344: 3338: 3334: 3329: 3328: 3319: 3317: 3315: 3313: 3311: 3309: 3294:on 2016-06-03 3290: 3286: 3282: 3278: 3274: 3270: 3266: 3262: 3258: 3257: 3249: 3242: 3234: 3228: 3210: 3206: 3202: 3198: 3194: 3190: 3186: 3181: 3180: 3177: 3173: 3168: 3163: 3159: 3155: 3151: 3144: 3136: 3132: 3127: 3122: 3118: 3114: 3110: 3106: 3102: 3098: 3094: 3087: 3079: 3075: 3071: 3067: 3063: 3059: 3055: 3051: 3047: 3043: 3035: 3019: 3015: 3011: 3004: 2996: 2992: 2988: 2984: 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Med. Genet 2760: 2752: 2748: 2744: 2740: 2736: 2732: 2728: 2724: 2717: 2709: 2705: 2701: 2697: 2693: 2689: 2682: 2674: 2670: 2665: 2660: 2656: 2652: 2648: 2644: 2640: 2633: 2625: 2621: 2616: 2611: 2607: 2603: 2600:(3): 234–43. 2599: 2595: 2591: 2584: 2570:on 2007-09-21 2569: 2565: 2561: 2555: 2540: 2536: 2532: 2528: 2524: 2520: 2513: 2498: 2494: 2487: 2479: 2475: 2470: 2465: 2461: 2457: 2453: 2446: 2431: 2427: 2426: 2421: 2415: 2399: 2393: 2385: 2381: 2377: 2373: 2368: 2363: 2359: 2355: 2351: 2344: 2342: 2333: 2327: 2323: 2316: 2302:on 2016-03-04 2301: 2297: 2291: 2275: 2271: 2265: 2250: 2246: 2242: 2241: 2236: 2230: 2215: 2211: 2207: 2206: 2201: 2195: 2187: 2183: 2179: 2175: 2171: 2167: 2160: 2152: 2146: 2130: 2126: 2122: 2116: 2101: 2097: 2093: 2086: 2071: 2067: 2066:Go Ask Alice! 2063: 2057: 2050: 2046: 2042: 2038: 2034: 2030: 2026: 2019: 2011: 2007: 2002: 1997: 1992: 1987: 1983: 1979: 1976:(9): e25239. 1975: 1971: 1967: 1963: 1956: 1954: 1952: 1936: 1932: 1928: 1922: 1914: 1908: 1904: 1897: 1882: 1878: 1874: 1868: 1853: 1849: 1845: 1839: 1824: 1820: 1819: 1813: 1805: 1798: 1794: 1791: 1786: 1777: 1762: 1758: 1752: 1745: 1739: 1732: 1728: 1725: 1720: 1716: 1705: 1702: 1700: 1697: 1695: 1692: 1690: 1687: 1685: 1682: 1680: 1677: 1675: 1672: 1670: 1667: 1665: 1662: 1660: 1657: 1655: 1652: 1650: 1647: 1645: 1642: 1640: 1637: 1635: 1632: 1630: 1627: 1626: 1619: 1615: 1612: 1608: 1602: 1598: 1596: 1592: 1591:DNA profiling 1587: 1583: 1578: 1574: 1562: 1559: 1551: 1541: 1535: 1534: 1530: 1525:This section 1523: 1514: 1513: 1505: 1502: 1498: 1493: 1483: 1481: 1470: 1468: 1466: 1462: 1458: 1454: 1453:heterogonesis 1450: 1446: 1442: 1441:Nicholas Fisk 1438: 1433: 1431: 1427: 1424:. One was an 1423: 1415: 1411: 1406: 1402: 1400: 1396: 1395:heterogonesis 1392: 1388: 1383: 1374: 1372: 1368: 1362: 1360: 1349: 1347: 1343: 1339: 1333: 1323: 1321: 1306: 1304: 1300: 1299:environmental 1296: 1295:psychological 1292: 1288: 1281: 1271: 1269: 1265: 1255: 1253: 1249: 1240: 1237: 1228: 1226: 1222: 1212: 1207: 1197: 1195: 1191: 1187: 1177: 1175: 1171: 1161: 1159: 1155: 1144: 1142: 1136: 1126: 1124: 1120: 1116: 1112: 1105: 1095: 1093: 1089: 1085: 1081: 1072: 1068: 1064: 1059: 1049: 1047: 1043: 1038: 1031: 1016: 1012: 1005: 1002: 999: 996: 993: 992: 991: 989: 979: 977: 973: 969: 965: 961: 956: 954: 945: 942: 939: 936: 932: 928: 927: 926: 923: 915: 912: 910: 906: 902: 897: 895: 891: 887: 879: 878:Uttar Pradesh 876:, located in 875: 872: 869: 866:, located in 865: 862: 860: 856: 853: 852: 851: 848: 847:Josef Mengele 844: 840: 839:Cândido Godói 836: 832: 831:ethnic groups 828: 820: 819:Yoruba people 816: 812: 807: 802: 792: 790: 786: 781: 779: 774: 770: 756: 752: 751:coronal plane 748: 744: 738: 733: 729: 728:coronal plane 725: 721: 720:co-incubation 714: 709: 708: 702: 698: 696: 693: 691: 686: 684: 681: 680: 676: 674: 672: 668: 663: 660: 658: 655: 649: 645: 643: 640: 639: 635: 633: 631: 627: 622: 620: 616: 615:almost always 612: 611:amniotic sacs 606: 602: 600: 597: 596: 592: 591:fertilisation 588: 586: 582: 578: 577:amniotic sacs 574: 570: 566: 563: 562: 558: 555: 552: 551: 548: 546: 541: 539: 535: 530: 522: 518: 511: 509: 504: 501: 497: 493: 483: 480: 479: 474: 469: 466: 462: 457: 454: 449: 447: 443: 439: 435: 430: 427: 418: 417:amniotic sacs 414: 409: 400: 397: 393: 385: 383: 379: 374: 372: 368: 364: 354: 352: 348: 344: 340: 337: 333: 329: 320: 316: 314: 308: 306: 302: 298: 294: 289: 287: 283: 279: 275: 271: 267: 263: 259: 255: 252: 248: 244: 236: 228: 219: 217: 213: 209: 207: 203: 194: 191: 188: 187: 186: 183: 174: 172: 166: 164: 160: 156: 155:South America 152: 148: 144: 143:phytoestrogen 140: 136: 135:Yoruba people 126: 124: 120: 116: 112: 108: 104: 100: 95: 93: 89: 85: 81: 77: 73: 69: 65: 59: 56: 52: 48: 43: 37: 33: 19: 5598: 5540: 5523: 5462:. 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Retrieved 1751: 1743: 1738: 1719: 1704:Virtual twin 1634:Doppelgänger 1616: 1603: 1599: 1569: 1554: 1545: 1538:Please help 1533:verification 1526: 1497:cryptophasia 1489: 1476: 1469: 1434: 1418: 1380: 1363: 1358: 1355: 1335: 1317: 1303:human nature 1283: 1261: 1246: 1234: 1225:polycythemic 1217: 1186:birth weight 1183: 1167: 1150: 1138: 1107: 1076: 1033: 1013: 1009: 985: 975: 957: 949: 931:West African 924: 921: 913: 898: 893: 883: 826: 824: 782: 766: 763:Demographics 694: 687: 664: 661: 653: 651: 623: 621:have fused. 614: 608: 584: 556:Description 542: 531: 527: 517: 505: 489: 476: 470: 458: 450: 431: 426:fingerprints 422: 398: 394: 391: 375: 362: 360: 338: 335: 331: 327: 326: 317: 309: 290: 277: 273: 265: 253: 250: 246: 242: 241: 210: 205: 201: 198: 184: 180: 167: 132: 123:doppelgänger 117:. Unrelated 114: 106: 96: 87: 75: 63: 62: 5628:Mixed twins 5149:(1): 43–7. 5108:(1): 72–6. 4945:(1): 81–5. 4918:28 February 4887:28 February 4782:28 February 4149:. pp. 3433:J Perinatol 2425:EurekAlert! 2135:11 November 2125:China Daily 1669:Mixed twins 1501:Idioglossia 1382:Monozygotic 1342:mixed twins 1332:Mixed twins 1326:Mixed twins 1236:Stillbirths 1231:Stillbirths 1170:miscarriage 968:anovulation 894:monozygotic 657:monozygotic 619:blastocysts 581:monozygotic 494:twin fetus 328:Monozygotic 268:, form two 262:sperm cells 119:look-alikes 76:monozygotic 51:Scott Kelly 5643:Categories 5526:conditions 5464:2018-03-30 5449:2008-10-18 5429:2008-10-06 5396:2008-10-02 5258:2008-10-06 5225:Pediatrics 5008:2018-09-05 4813:2023-04-29 4697:2008-09-30 4649:2015-04-18 4569:2012-04-07 4280:2015-10-26 4270:BabyCentre 4251:2015-10-23 4222:2015-10-23 3966:2013-08-10 3872:23 October 3842:23 October 3812:23 October 3783:2009-08-06 3754:2009-08-06 3587:2008-09-29 3535:2008-09-29 3373:2008-10-10 3363:"Twinning" 3298:2016-05-03 3256:The Lancet 3248:"Twinning" 3215:7 February 2945:: 147–159. 2574:2008-09-30 2545:2008-10-02 2503:2007-03-22 2436:2019-08-05 2306:2013-09-16 2255:2008-10-02 2220:2008-10-02 2106:2022-04-07 2076:2022-04-07 1941:2022-04-07 1887:2008-09-29 1858:2008-09-29 1829:2008-09-29 1767:2016-06-16 1711:References 1689:Twin study 1679:Multiverse 1664:Look-alike 1548:March 2024 1371:karyotypes 1280:Twin study 929:She is of 500:polar body 465:epigenetic 442:phenotypes 438:aneuploidy 367:blastocyst 258:fertilized 218:of twins. 159:South Asia 129:Statistics 58:astronauts 5623:Chimerism 5355:Evolution 5339:123390922 5190:CiteSeerX 4687:172964621 4520:1469-493X 4457:: i4353. 4116:The Times 3625:1358-8702 3285:208792233 3117:1058-0468 3024:8 January 2995:230986741 2979:1546-1718 2376:1355-4786 1639:Evil twin 1577:ovulation 1529:citations 1412:breed in 1190:premature 1154:triploidy 1119:DNA tests 1111:mosaicism 1098:Chimerism 972:clomifene 827:dizygotic 811:ere ibeji 795:Ethnicity 791:in food. 636:Days 4-8 571:for two) 545:placentas 508:triploidy 388:Incidence 357:Mechanism 336:identical 274:dizygotic 251:fraternal 243:Dizygotic 107:singleton 88:dizygotic 72:pregnancy 68:offspring 5533:Zygosity 5375:15068359 5312:17576931 5253:20498737 5245:17766488 5173:23507167 5130:19112883 5122:10073913 5046:16690234 5002:Archived 4977:Archived 4850:17165045 4807:Archived 4776:Archived 4772:CBC News 4754:30811910 4563:Archived 4538:27075527 4481:27599496 4432:Archived 4428:BBC News 4409:22015878 4323:23062593 4274:Archived 4245:Archived 4216:Archived 4186:Archived 4120:Archived 4077:19195460 4069:18307076 4034:24304051 3960:Archived 3956:11931691 3917:45092501 3806:Archived 3748:Archived 3724:Archived 3699:Archived 3676:23862192 3633:36287045 3578:Archived 3574:11968567 3568:: 1–17. 3530:16779988 3493:Archived 3474:Archived 3455:16281049 3390:(2004). 3367:Archived 3277:12957099 3209:Archived 3205:85215225 3176:12571155 3135:22460080 3018:Archived 2987:33414551 2924:43894450 2891:40396458 2854:16009939 2787:24123875 2751:31844710 2743:11113914 2624:18669930 2539:Archived 2535:10589400 2497:Archived 2478:19217091 2430:Archived 2384:10336022 2274:Archived 2249:Archived 2214:Archived 2129:Archived 2100:Archived 2070:Archived 2045:18063108 2010:21980404 1970:PLOS ONE 1935:Archived 1933:. 1999. 1881:Archived 1852:Archived 1823:Archived 1793:Archived 1761:Archived 1727:Archived 1622:See also 1426:intersex 1422:chimeras 1410:Hereford 1359:in utero 1338:biracial 1141:parasite 1115:intersex 1071:Thailand 1046:chimeric 855:Igbo-Ora 626:placenta 605:placenta 573:chorions 434:genotype 413:placenta 301:siblings 282:siblings 278:biovular 212:Zygosity 206:in utero 202:in utero 115:multiple 66:are two 5664:Zoology 5659:Sibling 5599:in fetu 5383:9460009 5303:1904168 5280:Bibcode 5212:9176461 5165:1488855 4961:6540028 4908:Gannett 4877:Reuters 4858:3343267 4803:YouTube 4610:1013354 4529:6464533 4472:5013231 4400:3202294 4358:12 June 3909:7437372 3705:5 April 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