Risk of Cesarean Delivery for Women with Obesity Using a Standardized Labor Induction Protocol.

OBJECTIVE

We aimed to determine the risk of cesarean among women with obesity undergoing labor induction within a prospective trial that utilized a standardized labor protocol.

STUDY DESIGN

This was a secondary analysis of a randomized trial of induction methods. Term (≥37 weeks) women with intact membranes undergoing induction with an unfavorable cervix (Bishop's score ≤6 and dilation ≤2 cm) were included. The trial utilized a labor protocol that standardized induction and active labor management, with recommendations for interventions at particular time points. Only women with a recorded body mass index (BMI) at prenatal care start were included in this analysis. The primary outcome was cesarean delivery compared between obese (≥30 kg/m) and nonobese (<30 kg/m) women. Indication for cesarean was also evaluated.

RESULTS

A total of 465 women were included: 207 (44.5%) obese and 258 (55.5%) nonobese. Women with obesity had a higher risk of cesarean compared with women without obesity (33.3 vs. 23.3%,  = 0.02), even when adjusting for parity, weight change over pregnancy, and indication for induction (adjusted relative risk [aRR] = 1.79, 95% confidence interval [CI]: [1.34-2.39]). Compared with women without obesity, women with obesity had a higher risk of failed induction (47.8 vs. 26.7%,  = 0.01) without a difference in arrest of active phase ( = 0.39), arrest of descent ( = 0.95) or fetal indication ( = 0.32), despite adherence to a standardized labor protocol.

CONCLUSION

Compared with women without obesity, women with obesity undergoing an induction are at increased risk of cesarean, in particular a failed induction, even within the context of standardized induction management. As standardized practices limit provider variation in labor management, this study may support physiologic differences in labor processes secondary to obesity.

KEY POINTS

· Even with a standardized induction protocol, women with obesity are at higher risk of cesarean.. · In particular, women with obesity are at increased risk of cesarean for failed induction.. · These findings support a possible biologic relationship between obesity and failed induction..