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Am J Perinatol 2024; 41(S 01): e1989-e1995
DOI: 10.1055/a-2096-2277
Original Article

The Impact of Cervical Effacement at Time of Amniotomy in Patients Undergoing Induction of Labor

Rebecca R. Rimsza 
1   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Ultrasound, Washington University in St. Louis, St. Louis, Missouri
,
Jeannie C. Kelly
1   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Ultrasound, Washington University in St. Louis, St. Louis, Missouri
,
Antonina I. Frolova 
1   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Ultrasound, Washington University in St. Louis, St. Louis, Missouri
,
Anthony A. Odibo
1   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Ultrasound, Washington University in St. Louis, St. Louis, Missouri
,
Ebony B. Carter
1   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Ultrasound, Washington University in St. Louis, St. Louis, Missouri
,
Alison G. Cahill
2   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Dell School of Medicine, University of Texas at Austin, Austin, Texas
,
Nandini Raghuraman
1   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Ultrasound, Washington University in St. Louis, St. Louis, Missouri
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Abstract

Objective There is evidence to suggest that early amniotomy during induction of labor is advantageous. However, following cervical ripening balloon removal, the cervix remains less effaced and the utility of amniotomy in this setting is less clear. We investigated whether cervical effacement at the time of amniotomy impacts outcomes among nulliparas undergoing induction of labor.

Study Design This was a secondary analysis of a prospective cohort of singleton, term, nulliparous patients at a tertiary care center undergoing induction of labor and amniotomy. The primary outcome was completion of the first stage of labor. Secondary outcomes were vaginal delivery and postpartum hemorrhage. Outcomes were compared between patients with cervical effacement ≤50% (low effacement) and >50% (high effacement) at time of amniotomy. Multivariable logistic regression was used calculate risk ratios (RR) to adjust for confounders including cervical dilation. Stratified analysis was performed in patients with cervical ripening balloon use. A post hoc sensitivity analysis was performed to further control for cervical dilation.

Results Of 1,256 patients, 365 (29%) underwent amniotomy at low effacement. Amniotomy at low effacement was associated with reduced likelihood of completing the first stage (aRR: 0.87 [95% confidence interval, CI: 0.78–0.95]) and vaginal delivery (aRR: 0.87 [95% CI: 0.77–0.96]). Although amniotomy at low effacement was associated with lower likelihood of completing the first stage in all-comers, those who had amniotomy performed at low effacement following cervical ripening balloon expulsion were at the highest risk (aRR: 0.84 [95% CI: 0.69–0.98], p for interaction = 0.04) In the post hoc sensitivity analysis, including patients who underwent amniotomy at 3- or 4-cm dilation, low cervical effacement remained associated with a lower likelihood of completing the first stage of labor.

Conclusion Low cervical effacement at time of amniotomy, particularly following cervical ripening balloon expulsion, is associated with a lower likelihood of successful induction.

Key Points

  • Low cervical effacement at amniotomy was associated with lower rates of complete dilation.

  • Effacement at amniotomy is especially important for patients who had a cervical ripening balloon.

  • Providers should consider cervical effacement when timing amniotomy for nulliparous term patients.

Keywords

induction - amniotomy - nulliparous - cervical effacement

Note

This study was previously presented as poster no. 958 at the 42nd Annual Pregnancy Meeting, Society for Maternal-Fetal Medicine (February 4, 2022).




Publication History

Received: 28 February 2023

Accepted: 18 May 2023

Accepted Manuscript online:
19 May 2023

Article published online:
19 June 2023

© 2023. Thieme. All rights reserved.

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