The association of pregnancy and the development of obesity - results of a systematic review and meta-analysis on the natural history of postpartum weight retention

Objective: The magnitude of the contribution of childbearing to the development of obesity is not entirely understood. Published studies on postpartum weight retention focus on risk factors and clinical interventions. Pooled estimates of postpartum weight retention have not been reported. We summarized the existing evidence of the natural history of postpartum weight retention and estimated the extent of time after delivery that weight retention is attributable to pregnancy. Design: Systematic review and meta-analysis of qualitatively homogeneous studies. Data sources: Medline search of published studies between January 1995 and August 2005; bibliography of candidate studies. Review methods: Eligibility: Observational studies and control groups of randomized controlled trials. Independent review and data abstraction including study design, subject characteristics, women's weight and study quality by two reviewers. Meta-analysis of average postpartum weight retention at different points in time after delivery. Sensitivity analysis for study specific covariates using meta-regression. Results: Twenty-five studies describing 21 cohorts met eligibility criteria. Sixteen studies appeared homogeneous enough to be included in the meta-analysis. Average postpartum weight retention decreased continuously until 12 months postpartum (6 weeks: 2.42 (95% confidence interval (95% CI): 2.32-2.52) Body mass index (BMI), 6 months: 1.14 (95% CI: 1.04-1.25) BMI, 12 months: 0.46 (95% CI: 0.38-0.54) BMI). Postpartum weight retention was 0.46 BMI lower in studies with follow-up rate >= 80% at 6 weeks postpartum compared to studies with lower follow-up rate (P<0.01). Conclusion: Published studies consistently showed a decline in mean body weight within the first year postpartum. Data on body weight later than 12 months postpartum are scarce. The published evidence suggests a re-increase in body weight. As there are rather lifestyle-related than biological reasons for an increase in body weight after one year postpartum, we suggest using the term 'postpartum weight retention' exclusively within a limited period (for example, up to 12-18 months) postpartum.