Risk of cesarean delivery in nulliparous women at greater than 41 weeks’ gestational age with an unengaged vertex

OBJECTIVE: The purpose of this study was to determine whether an unengaged vertex significantly increased the risk of cesarean delivery in nulliparous patients at 41 weeks or greater. STUDY DESIGN: The medical records from all nulliparous patients greater than 41 weeks’ gestation delivered at a single institution were reviewed. Patients undergoing both spontaneous and induced labor were included. Multivariate analyses were used to compare the influence of admission fetal station versus induction of labor on the risk of cesarean delivery. RESULTS: Four hundred forty-eight nulliparous women at greater than 41 weeks’ gestation were delivered at our institution during the study period. Sixty-two percent of these patients underwent induction of labor. There was a statistically significant increase in cesarean delivery rate compared with station (6% of patients at -1 station, 20% at -2 station, 43% at -3 station, and 77% at -4 station; P=.001). Compared with patients with an engaged vertex, patients with an unengaged vertex had 12.4 times the risk of cesarean delivery. Most of the cesarean deliveries were performed for failure to progress. On the basis of multivariate analysis, the odds of cesarean delivery were better predicted by fetal station than induction of labor. CONCLUSION: Nulliparous patients at 41 weeks or greater with an unengaged vertex are 12.4 times more likely to be delivered by cesarean section than a patient with an engaged vertex.

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