Maternal BMI and preterm birth: A systematic review of the literature with meta-analysis

Maria Regina Torloni, Ana Pilar Betrán, Silvia Daher, Mariana Widmer, Siobhan M. Dolan, Ramkumar Menon, Eduardo Bergel, Tomas Allen, Mario Merialdi

Research output: Contribution to journalArticlepeer-review

173 Scopus citations


Objectives.To examine the association between high prepregnancy maternal body mass index BMI and the risk of preterm birth PTB. Methods.A systematic review of the literature. We included cohorts and case-control studies published since 1968 that examined the association between BMI and PTB of all types, spontaneous (s), elective and with ruptured membranes (PPROM) in three gestational age categories: general (<37 weeks), moderate (32-36 weeks) and very (<32 weeks) PTB. Results.20,401 citations were screened and 39 studies (1,788,633 women) were included. Preobese (BMI, 25-29.9) and obese I (BMI, 3034.9) women have a reduced risk for sPTB: AOR 0.85 (95% CI: 0.80-0.92) and 0.83 (95% CI: 0.75-0.92), respectively. Their risk for moderate PTB was 1.20 (95% CI: 1.04-1.38) and 1.60 (95% CI: 1.32-1.94), respectively. Obese II women (BMI, 35-40) have an increased risk for PTB in general (AOR=1.33, 95% CI: 1.12-1.57) moderate (AOR=2.43, 95% CI: 1.46-4.05) and very PTB (AOR=1.96, 95% CI: 1.66-2.31). Obese III women (BMI > 40) have an even higher risk for very PTB (AOR=2.27, 95CI: 1.762.94). High BMI does not modify the risk for PPROM and increases the risk for elective PTB. Conclusions.High maternal BMI may have different effects on different types of PTB.

Original languageEnglish (US)
Pages (from-to)957-970
Number of pages14
JournalJournal of Maternal-Fetal and Neonatal Medicine
Issue number11
StatePublished - Nov 2009
Externally publishedYes


  • Adiposity
  • Body mass index
  • Literature review
  • Meta-analysis
  • Obesity
  • Overweight
  • Premature birth
  • Preterm labor

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Obstetrics and Gynecology


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