The term multiple births refers to the presence of more than one fetus in the uterus.
The number of twin, triplet, and other multiple births has been increasing during the last two decades. About 1 of 70 to 80 deliveries involves more than one fetus. The following make women more likely to become pregnant with more than one fetus:
Carrying more than one fetus overstretches the uterus, and an overstretched uterus tends to start contracting before the pregnancy reaches full term. As a result, the babies are usually born prematurely and are small. In some cases, the overstretched uterus does not contract well after delivery, causing bleeding in the woman after delivery. Because the fetuses can be in various positions and presentations, vaginal delivery can be complicated. Also, the contraction of the uterus after delivery of the first baby may shear away the placenta of the remaining baby or babies. As a result, the baby or babies that follow the first may have more problems during delivery.
Carrying more than one fetus also increases the risk of problems for the woman. They include high blood pressure plus protein in the urine (preeclampsia), gestational diabetes, excessive bleeding at delivery (postpartum hemorrhage), the need for cesarean delivery, small newborns, and preterm delivery.
During pregnancy, ultrasonography is done to confirm the number of fetuses.
Because problems can result from multiple births, doctors may decide in advance whether to deliver twins vaginally or by cesarean. If the first twin is in an abnormal position (anything other than head first), cesarean delivery is used. Occasionally, the first twin is delivered vaginally, but a cesarean delivery is considered safer for the second twin. For triplets and other multiple births, a cesarean delivery is usually done.
Last full review/revision June 2013 by Julie S. Moldenhauer, MD