We assessed the effect of labor induction among parturients carrying macrosomic fetuses on the risk of a cesarean section (CS). The study population consisted of consecutive women with singleton fetuses weighing >/=4,000 g, delivered between 1988 and 1999. A comparison was made between parturients who delivered after labor induction and those who delivered without labor induction. The Mantel-Haenszel procedure was used to obtain the weighted odds ratios while controlling for confounding variables. During the study period, 4,755 women delivered macrosomic newborns in our institution. In 20% of the women (n = 951) labor was induced, while 80% of them (n = 3,804) delivered without labor induction. The women who delivered after labor induction were more likely to be nulliparous (18.0 vs. 10.0%; p < 0.001). In addition, these women had significantly higher rates of gestational diabetes (23.3 vs. 10.7%; p < 0.001), hypertensive disorders (10.1 vs. 5.3%; p < 0.001), hydramnios (17.4 vs. 9.9%; p < 0.001), and oligohydramnios (2.1 vs. 0.2%; p < 0.001). The CS rate was significantly higher among the patients who delivered after labor induction as compared with those in whom labor was not induced (17.8 vs. 11.9%; odds ratio 1.6, 95% confidence interval 1.3-1.9, p < 0.001). Stratified analysis using the Mantel-Haenszel technique was performed to control for confounders such as gestational diabetes, hypertensive disorders, previous CS, hydramnios, oligohydramnios, and nulliparity. None of these variables changed the significant association between induction of labor and CS. The induction of labor among women carrying macrosomic fetuses was found to be an independent risk factor for a CS.
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