Childbearing is not associated with young women’s long-term obesity risk

OBJECTIVE Contemporary childbearing is associated with greater gestational weight gain and postpartum weight retention than in previous decades, potentially leading to a more pronounced effect of childbearing on women's long-term obesity risk. Previous work on the association of childbearing with women's long-term obesity risk mostly examined births in the 1970s and 1980s and produced mixed results. The association of childbearing and obesity incidence in a diverse, contemporary sample of 2731 US women was estimated. METHODS Propensity-score (PS) matching was used for confounding control when estimating the effect of incident parity (1996-2001) on 7-year incident obesity (BMI≥30 kg/m(2) ) (2001-2008). RESULTS In the sample, 19.3% of parous women became obese, whereas 16.1% of unmatched nulliparous women did. After PS matching without and with replacement, the differences in obesity incidence were, respectively, 0.0 percentage points (ppts) (95% CI: -4.7 to 4.7) and 0.9 ppts (95% CI: -4.9 to 6.7). Results were similar in analyses of prevalent parity and obesity in 2008 (n = 6601) conducted to explore possible selection bias. CONCLUSIONS These results imply that, in contemporary US parous women in their late 20s and early 30s, childbearing may not increase obesity incidence.