A vanishing twin, also known as twin resorption, is a
fetus
A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Pren ...
in a multigestation pregnancy that dies ''
in utero ''and is then partially or completely
reabsorbed. In some instances, the dead twin is compressed into a flattened, parchment-like state known as ''fetus papyraceus''.
Vanishing twins occur in up to one of every eight multifetus pregnancies and may not even be known in most cases.
"High resorption rates, which cannot be explained on the basis of the expected abortion rate, suggest intense fetal competition for space, nutrition, or other factors during early gestation, with frequent loss or resorption of the other twin(s)." Vanishing twin syndrome has been characterized as the loss of a twin before 12 weeks of gestation, or early during the first trimester where it is uncommon for twin pregnancy to have been identified.
According to Boklage, most twin pregnancies are ultimately born as singles, and vanished twins are a possible source of abnormal cells.
In one study, Boklage reported of 325 twin pregnancies, finding that only 61 ended as twins, with 125 ending as singletons; the remainder were lost. He has estimated that for every twin pair born, there are six singletons who survived a twin conception.
In pregnancies achieved by
''in vitro'' fertilization, "it frequently happens that more than one amniotic sac can be seen in early pregnancy, whereas a few weeks later there is only one to be seen and the other has 'vanished.
See also
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Chimera (genetics)
A genetic chimerism or chimera ( or ) is a single organism composed of cells of different genotype, genotypes. Animal chimeras can be produced by the fusion of two (or more) embryos. In plants and some animal chimeras, Mosaic (genetics), mos ...
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Mosaicism
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Parasitic twin
A parasitic twin, also known as an asymmetrical twin or unequal conjoined twin, occurs when a twin embryo begins developing in utero, but the pair does not fully separate, and one embryo maintains dominant development at the expense of the other. ...
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Runt
In a group of animals (usually a litter of animals born in multiple births), a runt is a member which is significantly smaller or weaker than the others.. Owing to its small size, a runt in a litter faces disadvantage, including difficulties in c ...
References
Further reading
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External links
Vanishing twin at eMedicine.com
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Health issues in pregnancy
Twin
Pregnancy with abortive outcome