Multifetal pregnancy is presence of > 1 fetus in the uterus.

Multifetal (multiple) pregnancy occurs in 1 of 70 to 80 deliveries. Risk factors include

• Ovarian stimulation (usually with clomiphene or gonadotropins)
• Assisted reproduction (eg, in vitro fertilization)
• Prior multifetal pregnancy
• Advanced maternal age

The overdistended uterus tends to stimulate early labor, causing preterm delivery (average gestation is 35 to 36 wk with twins, 32 wk with triplets, and 30 wk with quadruplets). Fetal presentation may be abnormal. The uterus may contract after delivery of the first child, shearing away the placenta and increasing risk for the remaining fetuses. Sometimes uterine distention impairs postpartum uterine contraction, leading to atony and maternal hemorrhage. Multifetal pregnancy increases the risk of preeclampsia, gestational diabetes, postpartum hemorrhage, cesarean delivery, preterm delivery, and growth restriction. Some complications develop only in multifetal pregnancies; an example is twin-twin transfusion syndrome (when twins share the same placenta and one twin receives more blood than the other).

Multifetal pregnancy is suspected if the uterus is large for dates; it is evident on prenatal ultrasonography. Cesarean delivery is done when indicated. Cesarean delivery is recommended for twins unless the presenting twin is in vertex presentation. Higher-order multiples are typically delivered by cesarean regardless of presentation. (see Abnormalities and Complications of Labor and Delivery: Cesarean Delivery).

Last full review/revision March 2013 by Julie S. Moldenhauer, MD