Concerning Pregnancy Weight Trends by Race and Ethnicity in the United States, 2016 to 2023

Background: Maternal prepregnancy body mass index (BMI) is a critical determinant of pregnancy outcomes, influencing risks for gestational diabetes, hypertensive disorders, cesarean delivery, stillbirth, and longterm maternal and child health. Although the overall rise in obesity among reproductive aged women in the United States is well recognized, recent national data describing detailed trends by race and ethnicity are limited. Objective: To examine temporal trends in prepregnancy BMI among U.S. mothers from 2016 to 2023, with a focus on changes in normal weight and obesity prevalence across racial and ethnic groups. Methods: We performed a retrospective analysis of nearly 30 million live births recorded in the CDC Natality database. Maternal BMI was categorized as underweight, normal weight, overweight, and obesity classes I to III. Race and ethnicity were defined using CDC conventions: non Hispanic (NH) White, NH Black, NH Asian, NH American Indian or Alaska Native, NH Native Hawaiian or Pacific Islander, NH more than one race, and Hispanic (all races). Annual prevalence for each BMI category was calculated, and linear regression was used to estimate slopes of annual change with 95% confidence intervals. Results: Nationally, normal weight prevalence declined from 42% in 2016 to 37% in 2023, while combined obesity increased from 24% to 29%. Declines in normal weight and corresponding increases in obesity were observed across all racial and ethnic groups. Asian mothers had the highest prevalence of normal weight (60% in 2016, 53% in 2023) and the lowest obesity prevalence (<15%), yet still showed significant annual increases. By 2023, obesity prevalence exceeded 30% among Black and American Indian/Alaska Native mothers and reached 25 to 30% among Hispanic and multiracial mothers. Hispanic and Black mothers experienced the steepest annual increases in obesity (+0.98% and +0.93% per year, respectively). Projections indicate that normal weight prevalence could fall below 30% within the next decade, while obesity prevalence may approach 40% by the mid 2030s. Conclusions: Between 2016 and 2023, U.S. mothers experienced a population wide redistribution from normal weight to obesity, affecting all racial and ethnic groups. These trends pose substantial risks for adverse pregnancy outcomes and threaten to exacerbate maternal health inequities. Equity focused preconception counseling, nutrition education, and policy level interventions are urgently needed.