- Fetal macrosomia, defined as a birth weight exceeding 4000 g, occurs in approximately 1 in 10 births in the United States. Recent studies have found that inducing labor increases the chance of cesarean section (CS) while not lowering the risk of complications of a macrosomic fetus. This study was an attempt to determine the impact of inducing labor on complications and outcomes. Subjects were 4755 consecutive women who delivered singleton fetuses weighing 4000 g or more in 1988-1999. One fifth of fetuses were delivered after inducing labor, whereas four fifths were born spontaneously. A Foley catheter was used to induce labor in 46.5% of women, oxytocin in 13%, and prostaglandin E 2 in 58%. Surgical induction was performed in 7% of cases. It was common for more than 1 method to be used. Women whose labors were induced tended to be of lower parity and to give birth to male infants. There were no significant differences between the induced and noninduced groups in maternal age, gestational age, or birth weight. Women in the induction group more often had mild preeclampsia, gestational diabetes, hydramnios, and oligohydramnios. Women having induction received epidural analgesia significantly more often than the others and were likelier to receive packed red blood cell transfusions. Induction was a risk factor for CS in both nulliparous and multiparous women; the odds ratios (ORs) were 1.9 and 1.4, respectively. CS was more frequently performed in women with and those without medical complications (ORs, 1.3 and 1.5, respectively). A significant association between induction of labor and CS persisted after controlling for possible confounding variables, including gestational diabetes, nulliparity, epidural analgesia, failure of labor to progress, and previous CS. On multivariate analysis, controlling for gestational age, induction of labor proved to be an independent risk factor for CS. The investigators conclude that, in women carrying a macrosomic fetus, inducing labor makes cesarean delivery more likely.