For women aged 35 years and older, induction of labor at 39 weeks neither raised nor lowered the rate of cesarean delivery, compared with expectant management, in a randomized clinical trial in the United Kingdom.
Labor induction at or before the due date may be beneficial in older women “because the gestational age at delivery that is associated with the lowest cumulative risk of perinatal death is 38 weeks.” However, induction in general is associated with an increased rate of cesarean delivery.
Previous studies of the relative benefits and harms of labor induction in this age group haven’t shed much light on the issue; they were small, observational in design, and were performed in the 1970s, so their findings may not be applicable to modern obstetric practice, wrote Dr. Kate F. Walker of University of Nottingham, England, and her associates.
They tested the hypothesis that labor induction at 39 weeks would reduce the rate of cesarean delivery in nulliparous women of advanced maternal age in the 35/39 Trial. It involved 619 women aged 35 years and older with singleton, uncomplicated pregnancies who were treated during a 2.5-year period at 39 secondary- and tertiary-care medical centers across the United Kingdom. The study participants were randomly assigned late in their pregnancies to either labor induction at 39 weeks (304 women) or expectant management (314 women).
The study hypothesis was not proven: there was no significant difference in the frequency of cesarean section between the induction group (32%) and the expectant management group (33%), for a relative risk of 0.99.
There also were no significant differences between the two study groups in maternal outcomes or neonatal outcomes (N Engl J Med. 2016 Mar 2;374:813-22. doi: 10.1056/NEJMoa1509117).
The trial did not address whether induction at 39 weeks’ gestation could prevent stillbirth, the researchers reported, but it provides support for the safety of performing a larger trial to test the effects of induction on stillbirths and other adverse neonatal outcomes.
The women assigned to labor induction did not differ from those assigned to expectant management in their subjective assessments of satisfaction with the childbirth experience. However, all the study participants had agreed to randomization. Women who had strong preferences about induction or expectant management, or strong feelings about their involvement in treatment decisions – and who may therefore have had a different take on their childbirth experience if labor were induced – were excluded from the study.
The study was supported by the National Institute for Health Research in the United Kingdom. Dr. Walker reported having no relevant financial disclosures; one of her associates reported ties to Roche Diagnostics, GlaxoSmithKline, General Electric, Chiesi, and Action Medical Research.