vanishing twin syndrome
A phenomenon where one twin in a multiple pregnancy is reabsorbed early in gestation, leaving a singleton pregnancy.
Full Definition
Vanishing twin syndrome refers to the spontaneous reduction of a multiple gestation to a singleton pregnancy through early embryonic or fetal demise and subsequent reabsorption. This occurs in approximately 10-15% of pregnancies that begin as twins, typically before 12 weeks gestation. The surviving twin usually develops normally, though there may be slightly increased risks of growth restriction or preterm delivery. Diagnosis is often made when early ultrasound shows two gestational sacs but later scans reveal only one viable fetus. The phenomenon may explain elevated maternal serum screening markers in some singleton pregnancies, as markers from the vanished twin may persist temporarily.
Usage
Usage note: No hyphenation in 'vanishing twin'; syndrome is not capitalized.
In Context
- "Early scan at 6 weeks showed dichorionic twins, but vanishing twin syndrome was diagnosed at 10 weeks." — Ultrasound report
- "The elevated MSAFP levels may be explained by vanishing twin syndrome earlier in pregnancy." — Maternal-fetal medicine consultation