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

Abstract

SummaryPost‐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.

Effects of maternal anthropometrics on pregnancy outcomes in South Asian women: a systematic review

“…In their recent review and meta‐analysis, Heslehurst et al . also found that in order to minimize bias, it was essential to include evidence from searches in addition to database searching .…”

“…Of the 22 included studies, 20 were identified through database search alone (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(42)(43)(44)(45)(46)48), one from screening the reference lists of relevant reviews (41) and one from searching the citations of included studies (47). In their recent review and meta-analysis, Heslehurst et al also found that in order to minimize bias, it was essential to include evidence from searches in addition to database searching (7).…”

“…Maternal obesity and both inadequate and excess GWG have been associated with adverse health outcomes for mother and infant . International research has highlighted that maternal obesity increases risks for both mother and child including gestational diabetes mellitus (GDM), pre‐eclampsia, gestational hypertension, depression, instrumental and caesarean birth, pre‐term and post‐term birth, large‐for‐gestational‐age babies, congenital anomalies and perinatal death . Maternal obesity has also been associated with longer‐term outcomes for the infant, such as subsequent obesity development and the associated life course morbidities .…”

Maternal body mass index and access to antenatal care: a retrospective analysis of 619,502 births in England

“…BMI is a significant predictor of maternal and perinatal health outcomes. For example, there is an increased risk of maternal and perinatal mortality, gestational diabetes, pre-eclampsia, pre- and post-term birth, stillbirth and congenital anomalies when mothers have a BMI in the overweight or obese ranges compared with women who have a BMI in the recommended range [ 7 , 14 – 19 ]. There are also increased risks for mothers with an underweight BMI, including preterm birth and miscarriage [ 20 – 22 ].…”

Is obesity in pregnancy associated with signs of chronic fetal hypoxia?

“…The multivariable linear regression model included the potential confounders maternal age and parity 19 . In addition, estimates were adjusted for the mediators gestational age and mode of delivery 20‐22 . An erythropoietin concentration ≥60 U/L was considered as high.…”