Unengaged vertex in nulliparous women in active labor: A risk factor for cesarean delivery

OBJECTIVE: To compare the route of delivery among nulliparous parturients with and without an engaged vertex in the early, active phase of labor. METHODS: Prospectively, the position of the fetal head was ascertained among nulliparous women at 37 weeks' gestation or more in early, active labor (cervical dilation ≤4 cm with adequate contractions). Sixteen variables, including maternal demographics, obstetric complications and intrapartum course, were examined using X ² and logistic regression analysis. RESULTS: Among the 77 patients, 33 (42.8%) had an unengaged vertex and 44 (57.2%) had an engaged vertex in active labor. Of the 22 cesarean deliveries for arrest disorder, 2 were in the engaged and 20 in the unengaged group (P <.001). The mean birth weight was similar among those who had vaginal (3,211 ± 416 g) and cesarean delivery (3,400±489 g, P= .08). Univariate analysis indicated that chorioamnionitis (relative risk [RR] 2.6, 95% confidence interval [CI] 1.4-4.9) and unengaged vertex (RR 13.3, CI 3.3-53.0) were associated with cesarean delivery for arrest disorders. When entered into a multiple logistic model, only unengagement in the early active was a risk factor for cesarean delivery. The following were not associated with cesarean delivery: maternal demographics, gestational age, estimate of fetal weight, presence or absence of meconium, preeclampsia, diabetes mellitus, private obstetric care or use of epidural anesthesia. CONCLUSION: Among nulliparous parturients, an unengaged vertex is a significant risk factor for cesarean delivery for arrest disorders.