title: Maternal body mass index and post-term birth: a systematic review and meta-analysis.
abstract: 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.
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: N
authors.initials: N
authors.lastname: Heslehurst
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: R
authors.initials: R
authors.lastname: Vieira
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: L
authors.initials: L
authors.lastname: Hayes
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: L
authors.initials: L
authors.lastname: Crowe
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: D
authors.initials: D
authors.lastname: Jones
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: S
authors.initials: S
authors.lastname: Robalino
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: E
authors.initials: E
authors.lastname: Slack
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: J
authors.initials: J
authors.lastname: Rankin
mesh_terms: D015992:Body Mass Index; D001835:Body Weight; D016208:Databases, Factual; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007233:Infant, Postmature; D009035:Mothers; D065228:Non-Randomized Controlled Trials as Topic; D009765:Obesity / Q000453:epidemiology*; D064887:Observational Studies as Topic; D011247:Pregnancy; D011248:Pregnancy Complications; D012959:Socioeconomic Factors
keywords: BMI; gestational age; maternal; obesity