Timing of Labor Induction Linked to Duration and Delivery Outcomes

Recent research has examined how the time of day when labor is induced may influence the length of labor and delivery outcomes. Several studies have analyzed data from thousands of pregnancies to identify patterns in labor duration related to induction timing.

Multiple retrospective analyses have reported that labor induction duration follows a circadian pattern, with the shortest average durations observed when induction begins in the early morning. For example, one study involving over 3,300 term pregnancies at a U.S. hospital found that inductions started at 05:00 averaged about 14.8 hours, while those started at 23:00 averaged around 21.0 hours.

Other research, including a preprint study of 3,688 induced labors, also identified a circadian rhythm in labor duration. This study found that maternal characteristics such as body mass index and parity influenced outcomes, but the shortest labors consistently occurred with early-morning inductions.

Additional findings from a study published in Molecular Metabolism, which included more than 2,300 pregnancies, indicated that women induced between early morning and noon experienced shorter labor durations than those induced near midnight. For patients with gestational diabetes, the difference in labor duration reached up to seven hours.

What the numbers show

• 3,363 pregnancies: 14.8 hours average labor when induced at 05:00, 21.0 hours at 23:00
• 3,688 induced labors: 14.7 hours at 05:00, 20.7 hours at 23:00
• 2,197 nulliparous women: 1.5 hours shorter labor for 6:00–11:59 a.m. induction

Analysis of the ARRIVE trial, which included 2,197 first-time mothers, found that elective induction starting between 6:00 a.m. and 11:59 a.m. was linked to a mean reduction in labor duration of about 1.5 hours compared to other times. This study found no difference in cesarean delivery rates based on induction timing.

In the retrospective cohort study at the U.S. hospital, early-morning inductions were associated with up to six hours shorter labor duration compared to late-evening inductions. The same study reported that these early-morning inductions were linked to reduced cesarean delivery rates, without an increase in adverse outcomes for newborns.

A review of randomized trials published by Cochrane compared morning and evening inductions and found no clear differences in maternal or neonatal outcomes. However, women in these trials showed a preference for morning induction when prostaglandins were used.

Across the reviewed studies, the timing of labor induction has been shown to influence the duration of labor, with early-morning starts generally resulting in shorter labors. These findings have been consistent across different patient populations and study designs, although the impact on other delivery outcomes has varied.

* This article is based on publicly available information at the time of writing.