Safety of misoprostol as a cervical ripening agent in vaginal birth after cesarean section

Modified Bishop's score and induction of labor in patients with a previous cesarean delivery

OBJECTIVES

The purpose of this study was to evaluate the association between preinduction modified Bishop's score and obstetric outcome, including successful vaginal birth after prior cesarean (VBAC) and uterine rupture in patients with a previous cesarean undergoing induction of labor.

STUDY DESIGN

Medical records of all patients who had an induction of labor after a previous cesarean in our institution between 1988 and 2002 were reviewed. Patients were divided into 4 groups according to the modified Bishop's score (0 to 2, 3 to 5, 6 to 8, and 9 to 12). The rates of successful VBAC, symptomatic uterine rupture, and other obstetric outcomes were evaluated in each group. Multivariate regression analyses were performed to adjust for confounding factors.

RESULTS

Out of 685 women included in the study, 187 (27.3%) had a modified Bishop's score <2, 276 (40.3%) of 3 to 5, 189 (27.6%) of 6 to 8, and 33 (4.8%) of 9 to 12. The rate of successful VBAC significantly correlated with the modified Bishop's score (57.5%, 64.5%, 82.5%, and 97.0%, respectively, P < .001). However, the rate of uterine rupture was not statistically significant between the groups (2.1%, 1.8%, 0.5%, 0.0%, P=.48). After adjusting for confounding variables, a modified Bishop's score >/=6 remained associated with successful VBAC (odds ratio [OR] 2.07, 95% CI 1.28-3.35, P < .001).

CONCLUSION

The modified Bishop's score before induction of labor is an independent factor associated with successful VBAC.

Randomized controlled trial of vaginal misoprostol versus dinoprostone vaginal insert for labor induction

OBJECTIVE

To compare the safety and efficacy of vaginal misoprostol versus dinoprostone vaginal inserts for cervical ripening and labor induction.

METHODS

Two hundred singleton gestations with an indication for cervical ripening and induction of labor were randomized to receive either 50 microg of misoprostol intravaginally every 3 h or a 10-mg dinoprostone vaginal insert every 12 h for a maximum of 24 h. Statistical analysis included Student's t test, the Mann-Whitney U test, chi2 analysis and Fisher's exact test.

RESULTS

Ninety-seven women received vaginal misoprostol while 89 women received the dinoprostone vaginal insert. Fourteen women were removed from the study after randomization. The interval from start of induction to vaginal delivery (794.5 +/-408 min vs. 1005.3 +/- 523 min; p < 0.02) was significantly shorter in the misoprostol group. Women receiving misoprostol were more likely to deliver vaginally both in < 12 h (44% vs. 12%; p < 0.0001) and < 24 h (68% vs. 38%; p < 0.001). A non-reassuring fetal heart rate tracing was the indication for 71.4% (20/28) of Cesarean deliveries in the misoprostol group compared to 40% (14/35) in the dinoprostone group (p = 0.03). There were no significant differences in neonatal outcomes.

CONCLUSION

Intravaginal misoprostol and dinoprostone are safe and effective medications for use in cervical ripening before labor induction. Misoprostol results in a shorter interval from induction to delivery. However, Cesarean delivery for a non-reassuring fetal heart rate tracing was more common with misoprostol.