The association between maternal body mass index (BMI), prolonged pregnancy (PP; 41 weeks gestation) and post-term birth (PTB; 42 weeks gestation): a systematic review with meta-analysis

Nicola Heslehurst, Rute Vieira, Louise Hayes, Lisa Crowe, Dan Jones, Shannon Robalino, Emma Slack, Judith Rankin

Research output: Contribution to journalAbstractpeer-review

Abstract

Introduction Prolonged pregnancy (PP) and post-term birth(PTB) are preventable causes of perinatal mortality, morbidity andobstetric complications. This systematic review investigates theassociation between maternal body mass index (BMI) and PP/PTB.Methods Database, citations and reference lists were searched.Screening and data extraction were carried out by two researchersindependently. Primary research published in English after 1990was included. Associations were investigated using dose–responseanalyses by computing study-specific linear trends and 95% CI.The overall odds ratio (OR) was calculated using a random-effectsmodel. A potential nonlinear relationship was assessed using cubicspline regression, and publication bias using Egger’s test.Results Searches identified 15 931 titles/abstracts: 39 wereincluded (n = 4 143 700 births). Most studies were publishedbetween 2005 and 2014 (n = 33), from Europe (n = 20), Middle-East/Asia (n = 9), USA (n = 5), Canada (n = 3), Australia (n = 1)and South Africa (n = 1). Meta-analyses were possible in 19 PTBstudies (n = 2 523 199), and ten PP studies (n = 441 346). Linearanalyses showed a significantly increased association between each5-unit BMI increase and PP (OR 1.13; 95% CI 1.04–1.22) andPTB (OR 1.18; 95% CI 1.11–1.26). The ORs of PTB increasedwith increasing obesity classifications: BMI 30–34.9 kg/m21.36;35.0–39.9 kg/m21.54; 40.0–44.9 kg/m21.72; 45.0–50 kg/m21.90.No significant publication bias was identified for either PTB(P = 0.60) or PP (P = 0.18).Conclusion This meta-analysis identified a significant associationbetween maternal obesity and PTB/PP. The results suggest thatthe odds of women with obesity having a PTB increases from36% to 90% depending on the obesity classification. Thedifferential association between the obesity classifications shouldbe considered when planning care to prevent adverse outcomesassociated with PTB.
Original languageEnglish
Pages (from-to)92
JournalBJOG-An International Journal of Obstetrics and Gynaecology
Publication statusPublished - 2016
EventBritish Maternal & Fetal Medicine Society (BMFMS) 18th Annual Conference 2016 -
Duration: 21 Apr 2016 → …

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