Trends and racial and ethnic disparities in prepregnancy obesity severity at first live birth in the US, 2015–2024: a population-based cross-sectional study

Prepregnancy obesity is a major modifiable risk factor for maternal cardiometabolic morbidity and contributes to maternal health disparities in the United States. Long-term adult obesity trends are well documented, but trajectories across the period temporally coinciding with the pandemic remain unclear. We assessed national trends in prepregnancy obesity by severity, age, and race and ethnicity among individuals at their first live birth in the United States from 2015 to 2024 and estimated the burden of adverse pregnancy outcomes associated with prepregnancy obesity. Using US National Vital Statistics natality files from January 1, 2015, to December 31, 2024, we analysed 13,793,888 individuals aged 15–44 years at their first live birth with singleton gestations. Age-standardized prevalence (per 1,000 first live births) and average annual percent changes (AAPCs) were modelled using joinpoint regression. Modified Poisson regression with robust error variance was used to estimate adjusted risk ratios (aRRs), and population attributable fractions (PAFs) were estimated by g-computation for a composite adverse pregnancy outcome. The age-standardized prevalence of prepregnancy obesity increased from 213.6 in 2015 to 275.2 per 1,000 first live births in 2024 (AAPC, 2.93% [95% CI, 2.79%-3.07%]). Joinpoint analysis identified a deceleration inflection in 2020 or 2021: for obesity overall the APC was 3.93% during 2015–2021 and 0.96% during 2021–2024, and for class 3 obesity 5.28% during 2015–2020 and 1.61% during 2020–2024. This deceleration was observed in non-Hispanic White, non-Hispanic Black, and Hispanic/Latina individuals. In contrast, non-Hispanic Asian individuals showed a sustained rapid increase (AAPC, 7.68%), particularly for class 3 obesity (AAPC, 12.18%). Class 3 obesity was associated with a higher risk of the composite adverse pregnancy outcome (2024 adjusted risk ratio, 1.69 [95% CI, 1.68–1.69]), and its population attributable fraction increased from 2.5% to 3.2%. Prepregnancy obesity remains a critical national challenge. Trends decelerated during the period temporally coinciding with the pandemic, but absolute prevalence increased in every racial and ethnic group and remained highest among NHOPI and AIAN individuals, while non-Hispanic Asian individuals showed a sustained rapid increase. Relative disparities narrowed even as absolute burden grew. Future efforts must combine structural policies addressing this persistent absolute burden with culturally tailored preconception care.