Multiple Births

The incidence of multiple gestations has increased with the increasing frequency of assisted reproduction. The frequency of higher-order multiple gestation has also increased significantly. Both perinatal and maternal morbidity and mortality are increased in these patients. These pregnancies are associated with a higher incidence of premature labor and delivery, abnormal presentation, preeclampsia, cord prolapse, need for operative delivery, uterine atony, and postpartum hemorrhage. Many of the maternal physiologic changes of pregnancy are exaggerated, which has significance for the anesthesiologist. FRC is greatly reduced because of the larger uterine size, and the reduced FRC results in a more rapid onset of hypoxemia during apnea or hypoventilation. In addition, aortocaval compression is more dramatic because of greater uterine weight and size. Uterine atony and the risk of postpartum hemorrhage are also greater than in singleton pregnancies. Depending on the fetal presentation, twins may be delivered vaginally; however, most obstetricians require vertex presentation of the presenting twin. If twin B has a nonvertex presentation, the obstetrician will perform either external cephalic version, breech extraction, or cesarean delivery. Epidural analgesia is useful in these situations because it can provide the necessary analgesia and be rapidly converted for use in an urgent cesarean section.