In a new report, researchers from UK say that delivery at 41 weeks increases risk of stillbirth without providing benefits to the neonate. That conclusion is from a systematic review of the literature reflecting 15 million pregnancies and nearly 18,000 stillbirths.
Published in PLoS Medicine, the analysis was based on a search of Medline, Embase, and Google Scholar from January 1990 to October 2018 with no language restrictions. Cohort studies on term pregnancies with estimates of stillbirths or neonatal deaths by gestational week were included.
All 13 studies assessed were from high-income countries, four looked at risks of stillbirth in white and black women, two enrolled women who were white and Asian, in five studies all the women were white, and in two studies all the mothers were black.
Review of the data showed that, from 37 to 42 weeks’ gestation, prospective risk of stillbirth increased with gestational age from 0.11 (95% CI 0.07 to 0.15) to 3.18 (95% CI 1.84 to 4.35) per 1,000 pregnancies. Risk of neonatal death increased significantly for delivery at 42 versus 41 weeks’ gestation (RR 1.87, 95% CI 1.07 to 2.86; P= 0.012). One additional stillbirth occurred for every 1,449 pregnancies that advanced from 40 to 41 weeks.
At between 38 and 41 weeks, the authors said, risks of newborn death were constant. They noted some limitations to the available literature, including variations in how low-risk pregnancy was defined, the wide time span of the studies, use of registry-based data, and potential confounders.