Maternal body mass index and post-term birth: a systematic review and meta-analysis

N Heslehurst* (Corresponding Author), R Vieira, L Hayes, L Crowe, D Jones, S Robalino, E Slack, J Rankin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)
10 Downloads (Pure)


Post-term birth is a preventable cause of perinatal mortality and severe morbidity. This review examined the association between maternal body mass index (BMI) and post-term birth at ≥42 and ≥41 weeks' gestation. Five databases, reference lists and citations were searched from May to November 2015. Observational studies published in English since 1990 were included. Linear and nonlinear dose-response meta-analyses were conducted by using random effects models. Sensitivity analyses assessed robustness of the results. Meta-regression and sub-group meta-analyses explored heterogeneity. Obesity classes were defined as I (30.0-34.9 kg m-2 ), II (35.0-39.9 kg m-2 ) and III (≥40 kg m-2 ; IIIa 40.0-44.9 kg m-2 , IIIb ≥ 45.0 kg m-2 ). Searches identified 16,375 results, and 39 studies met the inclusion criteria (n = 4,143,700 births). A nonlinear association between maternal BMI and births ≥42 weeks was identified; odds ratios and 95% confidence intervals for obesity classes I-IIIb were 1.42 (1.27-1.58), 1.55 (1.37-1.75), 1.65 (1.44-1.87) and 1.75 (1.50-2.04) respectively. BMI was linearly associated with births ≥41 weeks: odds ratio is 1.13 (95% confidence interval 1.05-1.21) for each 5-unit increase in BMI. The strength of the association between BMI and post-term birth increases with increasing BMI. Odds are greatest for births ≥42 weeks among class III obesity. Targeted interventions to prevent the adverse outcomes associated with post-term birth should consider the difference in risk between obesity classes.

Original languageEnglish
Pages (from-to)293-308
Number of pages16
JournalObesity Reviews
Issue number3
Early online date13 Jan 2017
Publication statusPublished - Mar 2017


  • Body Mass Index
  • Body Weight
  • Databases, Factual
  • Female
  • Gestational Age
  • Humans
  • Infant, Newborn
  • Infant, Postmature
  • Mothers
  • Non-Randomized Controlled Trials as Topic
  • Obesity
  • Observational Studies as Topic
  • Pregnancy
  • Pregnancy Complications
  • Socioeconomic Factors
  • Journal Article
  • Meta-Analysis
  • Review


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