The longer a pregnancy continues past 37 weeks gestation, the higher the risk of a stillbirth, according to a new meta-analysis published this week in PLOS Medicine by Shakila Thangaratinam of Queen Mary University of London, UK, and colleagues.
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Of the 3000 babies stillborn every year in the UK, a third appeared healthy at 37 weeks. In the new work, researchers searched major electronic databases for studies on term pregnancies that included weekly numbers of stillbirths or neonatal deaths. Thirteen studies, providing data on 15 million pregnancies and 17,830 stillbirths, were identified and included in their analysis.
The risk of stillbirth increased with gestational age from 0.11 stillbirths per 1000 pregnancies at 37 weeks (95% CI 0.07 to 0.15) to 3.18 stillbirths per 1000 pregnancies at 42 weeks (95% CI 1.84 to 4.35). From 40 to 41 weeks, there was a 64% increase in the risk of stillbirth. Neonatal mortality remained steady in babies born from 38 to 41 weeks, but was significantly higher for babies born at 42 weeks compared to 41 weeks (RR 1.87, 95% CI 1.07 to 2.86, p=0.012).
“Any mother considering prolongation of pregnancy beyond 37 weeks should be informed of the additional small but significantly increased risks of stillbirths with advancing gestation,” the authors say. “There is a need to assess the acceptability of early delivery at term to parents and healthcare providers to avoid the small risk of stillbirth. Better stratification of apparently low risk women for complications using individualized prediction models could reduce the number of women who need to be delivered to avoid one additional stillbirth.”
Khalil, A. et al. (2019) 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 Medicine. doi.org/10.1371/journal.pmed.1002838.