Childbearing is not associated with young women's long-term obesity risk
Funding agencies: WRR was supported by the University of Michigan Robert Wood Johnson Foundation Health and Society Scholar's small grant program, the National Cancer Institute (1K01CA172717-01), and University Cancer Research Funds at the Lineberger Cancer Center at UNC-Chapel Hill. We are also grateful to the Carolina Population Center (R24 HD050924) for general support. KJH was funded through a VA HSR&D QUERI Career Development Award (CDA 11-261) at the VA Greater Los Angeles and received additional support from the VA Office of Academic Affiliations. TS receives investigator-initiated research funding and support as Principal Investigator (R01 AG023178) from the National Institute on Aging at the National Institutes of Health. He also receives research funding as Principal Investigator of the UNC-DEcIDE center from the Agency for Healthcare Research and Quality. TS does not accept personal compensation of any kind from any pharmaceutical company, though he receives salary support from the Center for Pharmacoepidemiology and from unrestricted research grants from pharmaceutical companies (GlaxoSmithKline, Merck, Sanofi) to the Department of Epidemiology, University of North Carolina at Chapel Hill.
Disclosure: The authors declared no conflict of interest.
Author contributions: WRR conceived the research question, performed data analysis, interpreted results, and drafted the manuscript. MCC also performed data analysis and contributed to interpretation of results. KJH, TS, and AMSR contributed to interpretation of the findings and manuscript preparation.
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.
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/m2) (2001-2008).
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.
These results imply that, in contemporary US parous women in their late 20s and early 30s, childbearing may not increase obesity incidence.