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Vanishing Twin Syndrome - Loss of One Baby in a Multiple Pregnancy

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Updated January 15, 2009

Vanishing twin syndrome is a term for the disappearance of one developing baby in a multiple pregnancy. A mom might have an early ultrasound that detects two gestational sacs. But later on, only one fetal heartbeat is detectable and the second sac has disappeared (or one normally developing baby is present alongside a blighted ovum).

Some texts use the term "vanishing twin" for any pregnancy in which one baby in a multiple pregnancy is lost while the other survives, even if the twin has not technically vanished.

Statistics:

Research suggests that vanishing twin syndrome will occur in roughly a third of pregnancies in which an early ultrasound detects two or more developing babies. Researchers suspect, however, that vanishing twin syndrome may frequently occur without detection. Clinical estimates suggest that between 0.9% to 9.5% of pregnancies may begin as twin pregnancies even if only one baby is ultimately born.

In multiple pregnancies that have continued beyond 20 weeks, researchers estimate that about 2.6% of twin gestations and 4.3% of triplet gestations will be affected by fetal death.

Symptoms of Vanishing Twin Syndrome:

In very early cases of vanishing twin syndrome, the woman might never know that the condition occurred. In other cases, the loss of the twin might be accompanied by some miscarriage symptoms such as vaginal bleeding and hCG levels that rise more slowly than in normally developing twin pregnancies.

Causes:

Some cases of vanishing twin syndrome occur because of chromosomal abnormalities in the lost baby, but researchers do not fully understand why one twin is lost in other cases of vanishing twin syndrome. There's no reason to believe that the condition occurs because of anything the mother or anyone else does or does not do.

Complications for the Surviving Baby:

In most cases of vanishing twin syndrome, the surviving baby is not adversely affected.

Coping with Vanishing Twin Syndrome:

If you have been diagnosed with vanishing twin, you probably have a lot of mixed emotions. It's normal to grieve the baby you lost while also feeling relief that you are still pregnant with the viable baby. You should not feel that you have to pick and choose between your emotions. No rules say you cannot be sad and happy at the same time, and you shouldn't feel that you are dishonoring either baby if you go through a normal grieving process while continuing to eagerly anticipate your viable baby.

Sources:

Landy, H.J. and L.G. Keith, "The vanishing twin: a review. Human Reprouction Update 1998. Accessed 13 Apr 2008.

Johnson, Courtney D. and Jun Zhang, "Survival of Other Fetuses After a Fetal Death in Twin or Triplet Pregnancies." Obstetrics & Gynecology 2002. Accessed 13 Apr 2008.

Kelly, M.P., M.W. Molo, V.M. Maclin, Z. Binor, R.G. Rawlins and E. Radwanska, "Human chorionic gonadotropin rise in normal and vanishing twin pregnancies." Fertility and Sterility Aug 1991. Accessed 13 Apr 2008.

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