Prostaglandin versus mechanical dilation and the effect of maternal obesity on failure to achieve active labor: a cohort study

Purpose: Assess the impact of obesity on successful cervical ripening with mechanical versus prostaglandin ripening. Materials and methods: We compared obese to non-obese women in an analysis stratified by induction method, prostaglandin versus mechanical. Misoprostol dosing was the same for obese and non-obese women. Pitocin was titrated to effect. Our primary outcome was failure to achieve active labor. Secondary outcomes included overall cesarean delivery rate, doses of misoprostol used and need for protocol deviation. Results: Obese women had a higher cesarean delivery rate with misoprostol (35% versus 26%, p = 0.03) but not with mechanical ripening (31% versus 29%, p = 0.69). Obesity was associated with a higher rate of failure to achieve active labor in women undergoing prostaglandin ripening with misoprostol (24 versus 15%, p = 0.01) but not in women undergoing mechanical ripening (19 versus 15%, p = 0.55). After controlling for confounding variables, obese women who underwent cervical ripening with misoprostol had a higher rate of failure to achieve active labor, aOR 1.29 (95% CI: 1.00-1.67), which was not seen with mechanical ripening, aOR 1.09 (95% CI: 0.69-1.73). Conclusion: Obese women receiving the same dose of misoprostol as non-obese women have higher rates of failure to achieve active labor, an effect not seen with mechanical ripening.