Vanishing twin

A phenomenon in which one twin disappears in the womb during pregnancy

Vanishing twin syndrome is a phenomenon that occurs in a multiple pregnancy when one of the fetuses dies in the womb and is partially or completely reabsorbed by the mother or the surviving twin. This condition can occur at any time during pregnancy but is most common in the first trimester.

History

The concept of the vanishing twin was first recognized in 1945. With the advent of ultrasound technology, the phenomenon has been more frequently observed and documented. Early ultrasound scans can detect multiple gestations, but subsequent scans may reveal only one fetus, indicating the occurrence of a vanishing twin.

Causes

The exact cause of vanishing twin syndrome is not well understood. It is believed to be related to chromosomal abnormalities in the fetus, which can lead to miscarriage. Other factors may include improper implantation of the fertilized egg or issues with the placenta.

Diagnosis

Vanishing twin syndrome is often diagnosed through ultrasound. In early pregnancy, an ultrasound may show two gestational sacs, but later scans may reveal only one developing fetus. The presence of a vanishing twin can sometimes be confirmed by the detection of a second amniotic sac or fetal tissue.

Effects on the surviving twin

In most cases, the surviving twin is not affected by the loss of the other twin. However, there can be complications if the vanishing twin occurs later in pregnancy. These complications can include preterm labor, infection, or issues with the placenta.

Fetus papyraceus

A fetus papyraceus, a mummified fetus resulting from vanishing twin syndrome.

In some cases, the deceased twin may become compressed by the growing surviving twin and the uterine wall, resulting in a condition known as fetus papyraceus. This is a rare occurrence where the dead fetus is flattened and mummified.

Prevalence

Vanishing twin syndrome is relatively common, occurring in about 20-30% of multifetal pregnancies. However, many cases go undetected because they occur very early in pregnancy, often before the first ultrasound.

Related pages

• Multiple birth
• Miscarriage
• Ultrasound

References

• Landy, H. J., & Keith, L. G. (1998). The vanishing twin: A review. Human Reproduction Update, 4(2), 177-183.
• "Vanishing Twin Syndrome." American Pregnancy Association. Retrieved from [1]