Correspondence

Amniotomy in Labor

N Engl J Med 1993; 329:886-887September 16, 1993

Article

To the Editor:

In their recent paper on early amniotomy and the risk of dystocia in nulliparous women, Fraser et al. (April 22 issue)1 concluded that early amniotomy was effective in shortening labor and reducing the frequency of dystocia but did not lower the rate of cesarean section. Early amniotomy is only one component of active management of labor2. Unless early amniotomy is followed by early diagnosis of inefficient uterine action and treatment with appropriate doses of oxytocin, the cesarean-section rate may be unaffected.

In our hospital, amniotomy is performed when labor is diagnosed. We consider a rate of cervical dilatation of 1 cm per hour to reflect normal progress after amniotomy. If progress is unsatisfactory, oxytocin is given. In 1992, 1157 nulliparous women who each had a single fetus in cephalic presentation and who had entered spontaneous labor after a pregnancy of 38 weeks or more arrived at our hospital with intact membranes and a cervix that was dilated less than 6 cm. Their outcomes are shown in Table 1Table 1Oxytocin Therapy and Cesarean Section among Nulliparous Women with Spontaneous Labor and a Fetus in Cephalic Presentation..

With the implementation of all the components of active management of labor, including antenatal education, personal attention in labor, early treatment of inefficient uterine action, and early amniotomy, it is possible to decrease the rate of cesarean section as well as reduce the frequency of dystocia.

T.G. Teoh, M.R.C.O.G., M.S.C.
M.S. Robson, M.R.C.O.G., F.R.C.S.
P.C. Boylan, F.R.C.O.G., F.R.C.P.I.
National Maternity Hospital, Dublin 2, Ireland

2 References

1. 1

   Fraser WD, Marcoux S, Moutquin J-M, Christen A, Canadian Early Amniotomy Study Group. Effect of early amniotomy on the risk of dystocia in nulliparous women. N Engl J Med 1993;328:1145-1149
   Full Text | Web of Science | Medline

2. 2

   O'Driscoll K, Meagher D, eds. Active management of labour: the Dublin experience. 2nd ed. London: Bailliere Tindall, 1986.
   

Author/Editor Response

The authors reply:

To the Editor: The active management of labor, which originated at the National Maternity Hospital, is of interest precisely because it has been associated with low rates of cesarean section in case series1. Active management is a complex series of interventions, each component of which could be assessed for its effect on obstetrical outcome, including cesarean section. Although our study was designed to assess the effects of amniotomy on the occurrence of dystocia, other studies have attempted to examine other components of active management, including social support2,3 and the early administration of oxytocin4. Since our trial was not designed to assess possible effects of interactions between amniotomy and oxytocin or other components of active management, we cannot comment on these issues.

Cesarean section was not the main outcome of interest in our trial; however, we found no trend toward a reduction in the cesarean-section rate in association with early amniotomy. The estimate of the relative risk of cesarean section in the early-amniotomy group as compared with the control group was 1.1; the lower limit of the 95 percent confidence interval was 0.8. If our results represent a type II error, the maximal benefit that could be conferred by such a policy would be a 20 percent reduction in the cesarean-section rate. Even if amniotomy alone has no effect on the rate of cesarean section, that would not exclude the possibility that other components of active management, alone or in combination, could reduce the rate.

On the basis of current information, routine amniotomy, performed when the cervix is dilated 3 cm or more, is associated with a reduction in the duration of labor and a possible slight reduction in the frequency of oxytocin administration. Until evidence is available from randomized trials to indicate that early amniotomy results in a clinically important reduction in the risk of operative delivery, we are reluctant to advocate its routine use in clinical care.

William Fraser, M.D., M.Sc.
Sylvie Marcoux, M.D., Ph.D.
Jean-Marie Moutquin, M.D.
Laval University, Quebec, QC G1K 7P4, Canada

4 References

1. 1

   O'Driscoll K, Foley M, MacDonald D. Active management of labor as an alternative to cesarean section for dystocia. Obstet Gynecol 1984;63:485-490
   Web of Science | Medline

2. 2

   Hodnett ED, Osborn RW. Effects of continuous intrapartum professional support on childbirth outcomes. Res Nurs Health 1989;12:289-297
   CrossRef | Web of Science | Medline

3. 3

   Kennell J, Klaus M, McGrath S, Robertson S, Hinkley C. Continuous emotional support during labor in a US hospital: a randomized controlled trial. JAMA 1991;265:2197-2201
   CrossRef | Web of Science | Medline

4. 4

   Bidgood KA, Steer PJ. A randomized control study of oxytocin augmentation of labour. 1. Obstetric outcome. Br J Obstet Gynaecol 1987;94:512-517
   CrossRef | Medline