In vanishing twin syndrome, the prognosis for the remaining fetus is better if the loss occurs when?

• A. Earlier in the pregnancy
• B. Later in the pregnancy
• C. At term
• D. During the first year after birth

Answer: (A)

In vanishing twin syndrome, how the surviving fetus fares depends on when the other twin dies. If the loss happens early, the remaining fetus tends to have a better outcome because there is less time for the dead twin’s tissue to release inflammatory mediators and other factors into the maternal and fetal environment, and less disruption to placental function as the pregnancy progresses. Early loss means the placenta and maternal circulation can stabilize with fewer cascading effects such as growth restriction, preterm labor, or hemodynamic stress on the surviving twin. If the demise occurs later, these complications are more likely to affect the surviving fetus due to prolonged exposure to adverse inflammatory and circulatory changes, increasing risks for adverse outcomes.