Risks of stillbirth and neonatal death with advancing gestation at term: A systematic review and meta-analysis of cohort studies of 15 million pregnancies

Abstract

Background Despite advances in healthcare, stillbirth rates remain relatively unchanged. We conducted a systematic review to quantify the risks of stillbirth and neonatal death at term (from 37 weeks gestation) according to gestational age. Methods and findings We searched the major electronic databases Medline, Embase, and Google Scholar (January 1990–October 2018) without language restrictions. We included cohort studies on term pregnancies that provided estimates of stillbirths or neonatal deaths by gestation week. We estimated the additional weekly risk of stillbirth in term pregnancies that continued versus delivered at various gestational ages. We compared week-specific neonatal mortality rates by gestational age at delivery. We used mixed-effects logistic regression models with random intercepts, and computed risk ratios (RRs), odds ratios (ORs), and 95% confidence intervals (CIs). Thirteen studies (15 million pregnancies, 17,830 stillbirths) were included. All studies were from high-income countries. Four studies provided the risks of stillbirth in mothers of White and Black race, 2 in mothers of White and Asian race, 5 in mothers of White race only, and 2 in mothers of Black race only. The prospective risk of stillbirth increased with gestational age from 0.11 per 1,000 pregnancies at 37 weeks (95% CI 0.07 to 0.15) to 3.18 per 1,000 at 42 weeks (95% CI 1.84 to 4.35). Neonatal mortality increased when pregnancies continued beyond 41 weeks; the risk increased significantly for deliveries 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 (95% CI 1,237 to 1,747) pregnancies that advanced from 40 to 41 weeks. Limitations include variations in the definition of low-risk pregnancy, the wide time span of the studies, the use of registry-based data, and potential confounders affecting the outcome. Conclusions Our findings suggest there is a significant additional risk of stillbirth, with no corresponding reduction in neonatal mortality, when term pregnancies continue to 41 weeks compared to delivery at 40 weeks. Systematic review registration PROSPERO CRD42015013785

Induction of labour at 41 weeks versus expectant management and induction of labour at 42 weeks (SWEdish Post-term Induction Study, SWEPIS): multicentre, open label, randomised, superiority trial

“…The current practice in many centres in the United Kingdom and Scandinavia is to induce delivery no later than 42 weeks, but several studies suggest that the risk of perinatal mortality and morbidity has actually already increased significantly at 41 weeks 34 5 The risk of stillbirth increases gradually from 39 weeks of gestation13 and increases exponentially as the pregnancy approaches 42 weeks, 3-5 13 whereas the risk of neonatal mortality is not increased until 42 weeks according to most studies. 3-5 13 We therefore found it clinically justified to compare induction of labour at 41 weeks with expectant management and induction at 42 weeks for maternal and perinatal outcomes.…”

Interaction of chorioamnionitis at term with maternal, fetal and obstetrical factors as predictors of neonatal mortality: a population-based cohort study

“…Early term deliveries have been previously demonstrated to be associated with worse neonatal outcomes than full term deliveries (≥39 weeks) [ 11 ]. Similarly, the association between post-term deliveries and perinatal death has been established in Swedish, English and US population based cohort studies [ 7 , 12 – 15 ] as well as in a systematic review [ 15 ]. The positive interaction between chorioamnionitis and gestational age, found in our study even if preterm deliveries were excluded, could be explained by increased lung and brain susceptibility at gestational age less than 39 weeks.…”

Current Resources for Evidence‐Based Practice, November/December 2020

“…The push for initiating labor prior to 42 weeks’ gestation comes from the data showing increasing stillbirth rates with increasing gestational age. A meta‐analysis of 15 million births in high‐income countries found that per 1000 pregnancies, the stillbirth rate increased from 0.11 at 37 weeks’ gestation to 3.18 at 42 weeks’ gestation with one increased stillbirth between 40 and 41 weeks’ gestation with every 1449 pregnancies 2 . The analysis found no increase in neonatal deaths until after 41 weeks’ gestation.…”