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Am J Perinatol
DOI: 10.1055/a-2547-4196
Original Article

Association between Induction Start Time and Labor Duration in Nulliparous Women Undergoing Elective Induction of Labor

Francesca L. Facco
1   Department of Obstetrics and Gynecology, University of Pittsburgh, Pittsburgh, Pennsylvania
,
Cora MacPherson
2   The George Washington University Biostatistics Center, Washington, District of Columbia
,
Uma M. Reddy
3   Department of Obstetrics and Gynecology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
,
Alan T.N. Tita
4   Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama
,
Robert M. Silver
5   Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, Utah
,
Yasser Y. El-Sayed
6   Department of Obstetrics and Gynecology, Stanford University, Stanford, California
,
Ronald J. Wapner
7   Department of Obstetrics and Gynecology, Columbia University, New York, New York
,
Dwight J. Rouse
8   Department of Obstetrics and Gynecology, Brown University, Providence, Rhode Island
,
George R. Saade
9   Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas
,
John M. Thorp Jr
10   Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
,
Suneet P. Chauhan
11   Department of Obstetrics and Gynecology, University of Texas Health Science Center at Houston-Children's Memorial Hermann Hospital, Houston, Texas
,
Maged M. Costantine 
12   Department of Obstetrics and Gynecology, The Ohio State University, Columbus, Ohio
,
Edward K. Chien
13   Department of Obstetrics and Gynecology, Case Western Reserve University, Cleveland, Ohio
,
Kent D. Heyborne
14   Department of Obstetrics and Gynecology, University of Colorado, Denver, Colorado
,
Sindhu K. Srinivas
15   Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, Pennsylvania
,
Geeta K. Swamy
16   Department of Obstetrics and Gynecology, Duke University, Durham, North Carolina
,
William A. Grobman
17   Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois
,
for the Eunice Kennedy Shriver National Institute of Child Health Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network› Author Affiliations
Funding This work was supported by grants (UG 1HD40512, U24 HD36801, UG1 HD27869, UG1 HD34208, UG1 HD68268, UG1 HD40485, UG1 HD40500, UG1 HD53097, UG1 HD40560, UG1 HD40545, UG1 HD27915, UG1 HD40544, UG1 HD34116, UG1 HD68282, UG1 HD87192, UG1 HD68258, and UG1 HD87230) from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD; a list of other members of the NICHD MFMU Network is available in [Supplementary Material], available in the online version) and the National Center for Advancing Translational Sciences (UL1TR001873). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
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Abstract

Objective

This study aimed to examine the association between elective induction of labor (EIOL) start time and labor duration among nulliparous women.

Study Design

The ARRIVE trial was a multicenter randomized controlled trial of induction of labor at 390/7 to 394/7 weeks versus expectant management in low-risk nulliparous women. In this secondary analysis, we included participants randomized to the induction group who had an EIOL without spontaneous labor or rupture of membranes prior to the induction start. The start time of EIOL was categorized as: early a.m. (midnight to 5:59 a.m.), late AM (6 AM–11:59 a.m.), early p.m. (noon–5:59 p.m.), or late p.m. (6 p.m.–11:59 p.m.). The primary outcome was labor duration. Cesarean delivery rates by induction start time were also examined. Multivariable analysis was conducted controlling for age, body mass index, insurance status, and modified Bishop score on admission (<5 or ≥5).

Results

Of 3,062 women randomized to EIOL, 2,197 were included in this analysis. EIOL occurred in the early a.m. in 13%, in late a.m. in 28%, in early p.m. in 13%, and in late p.m. in 45%. Participants induced in the late a.m. had the shortest mean labor durations (21.5 ± 11.3 hours) and the highest frequency of delivery at < 24 hours (68%). In adjusted analyses, induction in the late a.m. (vs. grouped other time periods) remained significantly associated with shorter labor duration (−1.5 hours; confidence interval: −2.5 and −0.4; p = 0.006), and there was no interaction between Bishop score and time of EIOL. Cesarean delivery rates did not differ by start time.

Conclusion

Induction of labor starting between 6 a.m. and 11:59 a.m. was associated with shorter labor durations, independent of baseline maternal characteristics including cervical status on admission.

Key Points

  • Women were associated with shorter labor durations

  • Cesarean delivery rates did not differ by EIOL start time.

  • Differences in labor management by time of day may in part explain these findings.

Keywords

induction of labor - labor duration - elective induction

Supplementary Material



Publication History

Received: 12 February 2025

Accepted: 26 February 2025

Accepted Manuscript online:
27 February 2025

Article published online:
16 April 2025

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