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Obstetrics
Association of induction of labor and uterine rupture in women attempting vaginal birth after cesarean: a survival analysis

Presented as a poster at the 58th Annual Scientific Meeting of the Society for Gynecologic Investigation, Miami, FL, March 16-19, 2011.
https://doi.org/10.1016/j.ajog.2011.09.022Get rights and content

Objective

We sought to estimate the risk of uterine rupture associated with labor induction in women attempting trial of labor after cesarean (TOLAC) accounting for length of labor.

Study Design

This was a nested case-control study of women attempting TOLAC within a multicenter retrospective cohort study of women with a prior cesarean. Time-to-event analyses were performed with time zero defined as the first cervical exam of 4 cm. Subjects experienced the event (uterine rupture) or were censored (delivered).

Results

In all, 111 cases of uterine rupture were compared to 607 controls. When accounting for length of labor, the risk of uterine rupture in induced labor was similar to the risk in spontaneous-onset labor (hazard ratio, 1.52; 95% confidence interval, 0.97–2.36). An initial unfavorable cervical exam was associated with an increased risk of uterine rupture compared to spontaneous (hazard ratio, 4.09; 95% confidence interval, 1.82–9.17).

Conclusion

After accounting for labor duration, induction is not associated with an increased risk of uterine rupture in women undergoing TOLAC.

Section snippets

Materials and Methods

This is a nested case-control study conducted from 1996 through 2000 within a 17-center retrospective cohort study of pregnant women with at least 1 previous cesarean delivery. To identify factors associated with uterine rupture, all cases (women who attempted TOLAC and experienced uterine rupture) were matched on hospital site with 5 control subjects, chosen by a random number generator, who attempted TOLAC but did not have a uterine rupture. Institutional review board approval was obtained

Results

Within the retrospective cohort of 25,005 patients with a history of at least 1 prior cesarean delivery, 13,706 attempted TOLAC, and of those who attempted TOLAC, 134 experienced a uterine rupture (cases). At random, 670 of the 13,572 patients who attempted TOLAC but did not experience a uterine rupture were selected as controls. For this analysis of patients with only 1 prior cesarean, 111 cases and 612 controls were included. Cases and controls were similar with respect to maternal age,

Comment

When considering labor duration, we determined that women with 1 prior LTCS who undergo induction of labor are at similar risk of uterine rupture compared to women who present in spontaneous labor. When oxytocin exposure is considered, induction of labor and augmentation of labor have similar risks of uterine rupture, although both induction and augmentation of labor are associated with increased risk of uterine rupture compared to women who labor spontaneously. The initial cervical exam

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    Once 6 cm cervical dilation is reached and the active phase is entered, labor progress during induction of labor is similar to the patient in spontaneous labor; however, the duration of the phase before 6 cm dilation is longer in women undergoing induction of labor.20 More than half of induced women remained in the latent phase for 6 h, and nearly one-fifth remain in the latent phase for 12 h or longer.21 Also, women who are induced after cervical ripening have a markedly prolonged labor progression from 3 to 4 cm.

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This work was supported by a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (R01HD35631, G.A.M.). L.M.H. is supported by a grant from NICHD (T32HD055172; principal investigator, G.A.M.) and National Institutes of Health/National Center for Research Resources (UL1RR024992; principal investigator, Bradley Evanoff, MD, MPH).

The authors report no conflict of interest.

Reprints not available from the authors.

Cite this article as: Harper LM, Cahill AG, Boslaugh S, et al. Association of induction of labor and uterine rupture in women attempting vaginal birth after cesarean: a survival analysis. Am J Obstet Gynecol 2012;206:51.e1-5.

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