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Previous Volume 328:1145-1149 April 22, 1993 Number 16 Next

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ABSTRACT

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 randomization to full dilatation was 136 minutes shorter in the amniotomy group, and there was a trend toward less frequent use of oxytocin among the women assigned to amniotomy (36 percent vs. 41 percent; relative risk, 0.9; 95 percent confidence interval, 0.8 to 1.0). In a stratified analysis, the frequency of dystocia associated with amniotomy was reduced only among women with 3 cm initial dilatation. The cesarean-section rate was similar in the two groups (amniotomy, 12 percent; conservative management, 11 percent). There were no statistically significant differences in outcome between the infants delivered by the women in the two groups; the measures of an adverse outcome included admission to a neonatal intensive care unit, five-minute Apgar score below 7, and arterial cord-blood pH below 7.2.

Conclusions Early amniotomy is an effective method of shortening the duration of labor and reducing the frequency of dystocia among nulliparous women in labor, but it does not lower the rate of cesarean section.

Source Information

From the Departments of Obstetrics and Gynecology (W.D.F., J.-M.M.) and Social and Preventive Medicine (S.M., A.C.), Laval University, Quebec, Canada. The members of the study group are listed in the Appendix.

Address reprint requests to Dr. Fraser at DO-705-Perinatologie, Hopital St.-Francois d'Assise, 10 rue de l'Espinay, Quebec, QC G1L 3L5, Canada.

Full Text of this Article

Related Letters:

Amniotomy in Labor
Teoh T.G., Robson M.S., Boylan P.C., Fraser W., Marcoux S., Moutquin J.-M.
Extract | Full Text  
N Engl J Med 1993; 329:886-887, Sep 16, 1993. Correspondence

This article has been cited by other articles:

• Thornton, J G, Lilford, R J (1994). Active management of labour: current knowledge and research issues. BMJ 309: 366-9 [Abstract] [Full Text]  
• Teoh, T.G., Robson, M.S., Boylan, P.C., Fraser, W., Marcoux, S., Moutquin, J.-M. (1993). Amniotomy in Labor. NEJM 329: 886-887 [Full Text]  
• Parisi, V. M. (1993). Amniotomy in Labor -- How Helpful Is It?. NEJM 328: 1193-1195 [Full Text]