Morning Compared With Evening Induction of Labor: A Nested Randomized Controlled Trial

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To test the hypothesis that commencing induction of labor in the morning more closely reflects the physiologic timing of onset of labor and is associated with fewer women who remain undelivered 24 hours after cervical ripening and induction begins.


This was a nested randomized clinical trial, conducted between April 2001 and December 2004. Pregnant women at more than 36+6 weeks gestation with a cephalic presentation who were scheduled for prostaglandin induction of labor were eligible to participate. Women were randomly assigned to either admission in the morning (0800 hours) or admission in the evening (2000 hours). The primary outcome measures were vaginal birth not achieved in 24 hours, uterine hyperstimulation with associated fetal heart rate changes, and cesarean delivery.


A total of 620 women were entered in the trial, with 280 women in the morning admission group and 340 women in the evening admission group. There were no statistically significant differences between the timing of admission for induction and the primary trial outcomes. However, women admitted in the morning were less likely to require oxytocin infusion (morning admission 126 of 280 [45.0%] compared with evening admission 184 of 340 [54.1%]; relative risk 0.83, 95% confidence interval 0.70–0.97; P=.022). Nulliparous women admitted in the morning were less likely to require operative vaginal birth (morning admission 10 of 62 [16.1%] compared with evening admission 28 of 82 [34.2%]; relative risk 0.47, 95% confidence interval 0.25–0.90; P=.015).


For women who require induction of labor, consideration should be given to admission in the morning rather than admission in the evening.


Australian Clinical Trials Registry,, 12606000156583



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