What is Vanishing Twin Syndrome?

Vanishing Twin Syndrome is a medical phenomenon which affects some mothers carrying multiple fetuses. For unknown reasons, one or more of the fetuses may die and be fully reabsorbed by the body, leaving minimal traces behind, most typically in the first trimester of pregnancy. While the news media has drawn attention to Vanishing Twin Syndrome, creating an illusion of a rising rate, doctors suspect that the condition was probably simply not identified historically, and that increased monitoring during pregnancy has contributed to a rise in diagnoses of the condition.

The causes of Vanishing Twin Syndrome are not known. Sometimes, the condition may be the result of congenital malformations which are incompatible with life, or with lack of access to needed nutrients. For whatever reason, when the fetus dies, it is absorbed by the remaining sibling or siblings and the mother's body. Often, the mother may be totally unaware of the situation, although in some cases mild cramping and breakthrough bleeding occurs. In some rare cases, the dead fetus may become dessicated and compressed by its sibling or siblings, in which case it will be delivered in a flattened state, at whatever stage of development was reached before death. This is known as fetus papyraceus.

It is estimated that around 20 to 30 percent of multiple pregnancies are affected by Vanishing Twin Syndrome, although other members of the medical community have much higher and lower estimates. This means that many singletons actually started out as twins, and lost their siblings before birth. In some cases, Vanishing Twin Syndrome causes psychological problems in the surviving sibling, known as a twinless twin. Twinless twins sometimes experience confusion, guilt, loss, or other emotions which suggest that they were affected by the loss of their siblings.

Women over 30 appear to be at increased risk of vanishing twin syndrome, as are women who use hormones and other techniques to assist with reproduction. Commonly, vanishing twin syndrome goes unremarked, and it does not result in complications. When it is diagnosed, it is usually diagnosed as part of a routine follow-up ultrasound, in which a doctor notes that the two heartbeats from early pregnancy have dwindled to one.

When Vanishing Twin Syndrome is diagnosed, it can be traumatizing, but women should not blame themselves. Because the causes of the condition are so ambiguous, it's usually safe to say that nothing could have been done to prevent the loss of the fetus, and complications from this condition are rare. Some expecting parents choose to seek counseling to discuss the loss of the fetus, and their doctors can usually provide referrals for counseling services.