Early amniotomy, performed to induce labor despite a poor cervical score, remains widely practiced since first being introduced in the 18th century. Its effect on the duration of labor remains in dispute, although several randomized trials point to shorter labor. This study examined the effect of early artificial membrane rupture on the mode of delivery and pregnancy outcome in 338 women whose Bishop scores were 5. The comparison group included 1865 women admitted at term with premature rupture of membranes (PROM) 6 hours before the start of spontaneous uterine contractions. Twice as many women in the study group had a history of cesarean delivery (26 vs. 13 percent).Cesarean delivery was performed in 48 percent of the women having an amniotomy, compared with 19 percent of the control group with PROM, but the difference was significant only for those not having a previous cesarean delivery. Vacuum deliveries, however, were more frequent in the comparison group (3.1 vs. 0.9 percent). Lack of progress in labor during the first stage was three times more frequent in the amniotomy group, whereas a nonprogressive second stage of labor was insignificantly more common in the comparison group. Significantly more women with PROM received oxytocin because of prolonged or arrested dilatation. An abnormal fetal heart rate pattern was recorded during labor in 15 percent of the amniotomy group and in 8 percent of the PROM group. Two study subjects and one control subject had uterine rupture. There was no difference in the risk of chorioamnionitis. Early amniotomy remained an independent risk factor for operative delivery on multiple logistic analysis controlling for confounding variables. These findings imply that caution is needed when deciding to perform early surgical induction unless it is a final option or other approaches are contraindicated.Eur J Obstet Gynecol Reprod Biol 1999;86colon;145ndash;149
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