Postdates induction with an unfavorable cervix and risk of cesarean^*

Abstract

Objective: To determine the risk of cesarean delivery associated with postdates induction (≥41 weeks) compared to term induction (37–40w6d) among women with an unfavorable cervix, and to examine the risk factors associated with cesarean among women undergoing postdates induction.

Methods: A planned secondary analysis of a large prospective cohort study on induction (n = 854) was performed. Women with a singleton gestation, intact membranes, and an unfavorable cervix (Bishop score of ≤6 and dilation ≤2 cm) who were undergoing a term (≥37 weeks) induction for any indication were included. Women with a prior cesarean were excluded. The primary outcome was cesarean delivery. Relative risk of cesarean was estimated using a modified Poisson’s regression model.

Results: There was a significantly increased risk of cesarean for women undergoing postdates induction (n = 154) compared to women 37–40w6d (n = 700), (46.8 versus 26.0%, p < .001). This increased risk of cesarean remained after adjustment for race, parity, and pregnancy-related hypertension (aRR 1.70 [1.39–2.09], p < .001). Risk factors independently associated with cesarean among women ≥41 weeks included nulliparity (aRR 3.38 95%CI (2.42–4.74)), BMI ≥30 (aRR 1.72 95%CI (1.34–2.21)), and starting cervical dilation <1 cm (aRR 1.37 95%CI (1.11–1.70)).

Conclusions: Women ≥41 weeks undergoing an induction with an unfavorable cervix are at a significantly increased risk of cesarean compared to women 37–40w6d, with nulliparity, obesity, and cervical dilation <1 cm being independent risk factors. These data can be used to augment patient counseling and support the ongoing discussion regarding the risk of post dates induction.

Keywords:

• Postdates
• induction
• cesarean

Disclosure statement

Lisa D. Levine provided consultant work for Sudler and Hennessey on labor induction which is unrelated to this work.

Additional information

Funding

This work was funded in part by a career development award in Women’s Reproductive Health Research [Office of Research on Women’s Health: K12-HD001265-16].