Physical activity during pregnancy stratified by body mass index: A focus on class 3 obesity

The prevalence of pre-pregnancy obesity, including pre-pregnancy class 3 obesity, has increased over time, with significant implications for maternal and neonatal well-being. Regular physical activity may mitigate these risks. Available data suggest that most pregnant individuals do not meet the recommended physical activity guidelines of accumulating at least 150 min of moderate-intensity exercise per week. Importantly, limited data are available regarding physical activity patterns in individuals with higher body mass index (BMI), particularly for those with class 3 obesity (BMI ≥ 40 kg/m²). The aim of this study was to evaluate whether pregnant individuals are meeting physical activity guidelines. We assessed self-reported physical activity across BMI categories including those with class 3 obesity, further subdivided into BMI of 40-49.9 and ≥ 50 kg/m ².

This is a retrospective cohort study of individuals at an academic hospital system who delivered between May 1, 2018 and May 1, 2023. To be included, individuals had to respond to the following two-item physical activity questionnaire early in pregnancy: (1) "On average, how many days per week do you engage in moderate to strenuous exercise?" And (2) "On average, how many minutes do you engage in exercise at this level?" From these two questions, total minutes per week of activity were calculated. Individuals met physical activity guidelines if they engaged in ≥ 150 min of physical activity per week. Data were analyzed using Kruskal-Wallis and Chi-square tests.

A total of 6884 individuals were incl uded in the cohort. A total of 510 individuals met the criteria for class 3 obesity, with 61 having a pre-pregnancy BMI ≥ 50 kg/m ². Among normal weight individuals (BMI 18.5-24.9 kg/m ²), 34% met physical activity guidelines. Overweight and obese individuals were significantly less physically active than those with normal BMI (p < 0.05). Only 22% of those with BMI 40-49.9 kg/m ² and 18% of those with BMI ≥ 50 kg/m ² reported sufficient physical activity.

Our results are consistent with existing data, showing that pregnant individuals are not meeting physical activity goals. Pregnant individuals who are overweight or obese engage in significantly less physical activity compared to those with a BMI in the normal range, with the lowest levels of activity observed among individuals with class 3 obesity. More data are needed on physical activity among pregnant individuals with class 3 obesity, including evaluation of potential interventions to increase activity as well as barriers to participation. Increasing physical activity in this group may positively impact both maternal and neonatal health.