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Obstetrics
The efficacy of early amniotomy in nulliparous labor induction: a randomized controlled trial

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Objective

The purpose of this study was to assess whether early amniotomy reduces the duration of labor or increases the proportion of subjects who are delivered within 24 hours in nulliparous patients who undergo labor induction.

Study Design

We performed a randomized controlled trial that compared early amniotomy to standard management in nulliparous labor inductions. Inclusion criteria were nulliparity, singleton, term gestation, and a need for labor induction. Subjects were assigned randomly to early amniotomy (artificial rupture of membranes, ≤4 cm) or to standard treatment. There were 2 primary outcomes: (1) time from induction initiation to delivery and (2) the proportion of women who delivered within 24 hours.

Results

Early amniotomy shortens the time to delivery by >2 hours (19.0 vs 21.3 hours) and increases the proportion of induced nulliparous women who deliver within 24 hours (68% vs 56%). These improvements in labor outcomes did not come at the expense of increased complications.

Conclusion

Early amniotomy is a safe and efficacious adjunct in nulliparous labor inductions.

Section snippets

Methods

We performed an unblinded, randomized controlled trial at Washington University in St. Louis and the University of Pennsylvania with approval from the Institutional Review Boards at both institutions. Inclusion criteria for this clinical trial were nulliparity, singleton, term gestation (defined as >37 weeks 0 days), and a need for labor induction as determined by the treating physician. Exclusion criteria included HIV infection or cervical dilation of >4 cm at admission examination.

Eligible

Results

Seven hundred forty-nine women were screened for eligibility; 84 women (11.2%) were deemed ineligible by exclusion criteria. Of the 635 eligible nulliparous women, 585 women (92%) consented and were assigned randomly (Figure); 292 women were assigned to the early amniotomy group, and 293 women were assigned to standard treatment. Those who agreed to participate and those who did not were similar in terms of baseline characteristics (age, gestational age, preexisting medical conditions). The

Comment

The goal of our study was to assess the efficacy and safety of early amniotomy in nulliparous women who undergo labor induction. The results of this clinical trial indicate that early amniotomy shortens labor by approximately 2 hours, increases the proportion of women delivered within 24 hours, but does not impact the rate of cesarean deliveries. Although these differences in duration of labor and proportion of women delivered within 24 hours may seem to be intermediate outcomes, we would argue

References (17)

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    Citation Excerpt :

    This trial used a cervical dilation cutoff of ≤4 cm to differentiate early amniotomy from standard management, which can be highly dependent on the individual examiner. Furthermore, Macones et al21 included a diverse range of both single and combination pharmacologic and mechanical induction methods with varying effectiveness.2 This study used a uniform combination of pharmacologic cervical ripening with Foley catheter placement for all enrolled patients.

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The authors report no conflict of interest.

Cite this article as: Macones GA, Cahill A, Stamilio DM, et al. The efficacy of early amniotomy in nulliparous labor induction: a randomized controlled trial. Am J Obstet Gynecol 2012;207:403.e1-5.

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