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PLoS Med. 2019 Jul 2;16(7):e1002838. doi: 10.1371/journal.pmed.1002838. eCollection 2019 Jul.

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

Author information

1
Women's and Sexual Health Division, University Hospital Lewisham, Lewisham and Greenwich NHS Trust, London, United Kingdom.
2
Women's Division, North Middlesex University Hospital, London, United Kingdom.
3
Clinical Biostatistics Unit, Hospital Ramon y Cajal (IRYCIS) and CIBER Epidemiology and Public Health (CIBERESP), Madrid, Spain.
4
Dugald Baird Centre for Research on Women's Health, Aberdeen Maternity Hospital, University of Aberdeen, Aberdeen, United Kingdom.
5
University of Malaya, Kuala Lumpur, Malaysia.
6
Fetal Medicine Unit, St George's University Hospitals NHS Foundation Trust, London, United Kingdom.
7
Molecular and Clinical Sciences Research Institute, St George's University of London, London, United Kingdom.
8
Barts Research Centre for Women's Health, Women's Health Research Unit, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom.
9
Multidisciplinary Evidence Synthesis Hub, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom.

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.

Conflict of interest statement

The authors have declared that no competing interests exist.

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