Healthy first-time mothers whose labour was induced in the 39th week of pregnancy were less likely to deliver by Caesarean section, compared to those who waited for labour to begin naturally, according to a study funded by the National Institutes of Health. Researchers also found that infants born to women induced at 39 weeks were no more likely to experience stillbirth, new-born death or other severe complications, compared to infants born to un-induced women.
“Prior to this study, there was concern that induction of labour would increase the chance of caesarean delivery,” said study author Dr Uma M Reddy, of the pregnancy and perinatology branch of NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “Our analysis suggests that elective induction at 39 weeks is associated with a lower rate of caesarean delivery and does not increase the risk of major complications for new-borns.”
Although caesarean delivery is safe for mother and baby, it is major surgery and does carry risks. It takes longer to recover from a C-section, compared to vaginal birth, and the surgery may increase the risk of problems with vaginal birth in future pregnancies.
Elective induction – labour induced when there is no medical need to do so – before 39 weeks (link is external) is known to pose health risks for new-borns. However, elective induction at 39 weeks, or one week before the due date, has become more common in recent years, said Reddy. NICHD funded the current study to determine the potential risks and benefits of elective induction at 39 weeks, compared to expectant management, or waiting for labour to begin naturally, with health care practitioners intervening if problems occur.
The study enrolled more than 6,000 pregnant women at 41 hospitals participating in the NICHD-supported Maternal-Foetal Medicine Units Network. Roughly half of the women were assigned at random to have their labour induced in the 39th week of pregnancy; the remaining women received expectant management.
The researchers compared births between the two groups in terms of a primary outcome, a composite measure that included death of the baby during or after birth; the new-born’s need for respiratory support; seizure, infection, birth trauma (injury) or haemorrhage; and other birth complications.
The primary outcome occurred in 4.3% of the induced labour group and 5.4% of the expectant management group, a difference that was not statistically significant. However, the proportion of caesarean delivery was significantly lower for the induced group (18.6%), compared to the other group (22.2%). Similarly, the rate of blood pressure disorders of pregnancy was significantly lower in women who were induced (9.1%), compared to the other group (14.1%).
The researchers estimate that one caesarean delivery could be avoided for every 28 low-risk, first-time mothers undergoing elective induction at 39 weeks.
Background: The perinatal and maternal consequences of induction of labor at 39 weeks among low-risk nulliparous women are uncertain.
Methods: In this multicenter trial, we randomly assigned low-risk nulliparous women who were at 38 weeks 0 days to 38 weeks 6 days of gestation to labor induction at 39 weeks 0 days to 39 weeks 4 days or to expectant management. The primary outcome was a composite of perinatal death or severe neonatal complications; the principal secondary outcome was cesarean delivery.
Results: A total of 3062 women were assigned to labor induction, and 3044 were assigned to expectant management. The primary outcome occurred in 4.3% of neonates in the induction group and in 5.4% in the expectant-management group (relative risk, 0.80; 95% confidence interval [CI], 0.64 to 1.00). The frequency of cesarean delivery was significantly lower in the induction group than in the expectant-management group (18.6% vs. 22.2%; relative risk, 0.84; 95% CI, 0.76 to 0.93).
Conclusions: Induction of labor at 39 weeks in low-risk nulliparous women did not result in a significantly lower frequency of a composite adverse perinatal outcome, but it did result in a significantly lower frequency of cesarean delivery.
William A Grobman, Madeline M Rice, Uma M Reddy, Alan TN Tita, Robert M Silver, Gail Mallett, Kim Hill, Elizabeth A Thom, Yasser Y El-Sayed, Annette Perez-Delboy, Dwight J Rouse, George R Saade, Kim A Boggess, Suneet P Chauhan, Jay D Iams, Edward K Chien, Brian M Casey, Ronald S Gibbs, Sindhu K Srinivas, Geeta K Swamy, Hyagriv N Simhan, George A Macones
[link url="https://www.nih.gov/news-events/news-releases/induced-labor-39-weeks-may-reduce-likelihood-c-section-nih-study-suggests"]NIH material[/link]
[link url="https://www.nejm.org/doi/full/10.1056/NEJMoa1800566?query=featured_home"]New England Journal of Medicine abstract[/link]