Effect of early amniotomy on the risk of dystocia in nulliparous women

Background Early amniotomy has been advocated as a means of preventing dystocia, but its efficacy has not been studied prospectively. The purpose of this multicenter study was to determine whether routine early amniotomy reduces the risk of dystocia for nulliparous women in spontaneous labor. Methods We studied 925 nulliparous women in labor, who were stratified according to the degree of cervical dilatation (<3 cm vs. ≥ 3 cm) and randomly assigned to either early rupture of the membranes (amniotomy group) or conservative management of labor (conservative-management group). Dystocia was defined as a period of at least four hours after dilatation of the cervix to 3 cm had been reached during which the mean rate of cervical dilatation was less than 0.5 cm per hour. Results Dystocia was significantly less frequent in the amniotomy group than in the conservative-management group (34 percent vs. 45 percent; relative risk, 0.8; 95 percent confidence interval, 0.6 to 0.9). The median length of time from randomiz...