The Vanishing Twin: An Explanation for Discordance Between Chorionic Villus Karyotype and Fetal Phenotype

Reddy, M.B., K.S., Petersen, S.E., M.B., Antonarakis, S.E., Blakemore, K.J.

The proportion of multiple gestation sustaining a very early loss is as high as 63 and 71 per cent according to two other sonographic series (Levi, 1975: Schneider et al., 1979). Employing the 48 per cent figure, ‘vanishing twins’ might be expected in 1.6-2.6 per cent of pregnancies continuing as singletons.

Many women may experience a short interval of vaginal spotting or bleeding associated with the loss of a twin early in pregnancy. Very early sonography, at 6-8 weeks of gestation, would identify the majority of these as echolucencies suggestive of a degenerating twin sac or sometimes more clearly as an embryonic demise. Prenatal Diagnosis, Volume 11,679-684(1991)