Higher risk for perinatal death beyond 41 weeks' gestation than in earlier term pregnancy

Reference

Muglu J, Rather H, Arroyo-Manzano D, et al. Risks of stillbirth and neonatal death with advancing gestation at term: A systematic review and meta-analysis of cohort studies of 15 million pregnancies. PLoS Med 2019;16(7):e1002838.

Synopsis

This was a large, carefully designed, and carefully executed systematic review of cohort studies to evaluate the risks of stillbirth and neonatal death in low-risk term pregnancies on a week-by-week basis, starting at 37 completed weeks (37.0). The authors did a thorough literature search from 1990 to 2108. From among more than 10,000 citations, the authors selected 13 studies with more than 15 million pregnancies, 17,830 stillbirths, and 2348 neonatal deaths for inclusion. All were from high-income countries. Low-risk pregnancy was defined as a healthy woman with an apparently uncomplicated pregnancy who would be entering labor with a low risk of intrapartum complications. (The precise definitions varied from study to study.) The authors found that the risk of stillbirth rose gradually from 37.0 to 40.0 weeks' gestation, from approximately 0.1/1000 at 37.0 weeks to approximately 1.0/1000 at 40.0 weeks, then increased more rapidly. The risk of stillbirth rose significantly from 40.0 and 41.0 weeks' gestation (relative risk [RR] 1.64; 95% CI 1.51 - 1.77; P < .001), and rose even faster thereafter. The risk of neonatal death was relatively constant from 38.0 to 40.0 weeks and increased markedly from 40.0 to 41.0 weeks (RR 1.87; 1.07 - 2.86; P = .012). Of note is that women of black race were 1.5 to 2 times more likely to have a stillbirth than women of white race at all gestational ages. These observational data suggest that intervention to induce labor may be warranted at 40.0 weeks' gestation rather than the customary 41.0 weeks' gestation. Assessment of such interventions will necessarily require meta-analysis of many randomized controlled trials since the perinatal mortality outcome is relatively rare, though clearly catastrophic.