Higher BMI linked to reduced physical activity in pregnancy

Higher BMI linked to reduced physical activity in pregnancy | Image Credit: © Lisa Anastassiu - © Lisa Anastassiu - stock.adobe.com.

Physical activity goals are not being met by pregnant patients, especially those who are overweight or obese, according to a recent study published in Pregnancy.¹

An increase in the rate of obesity has been reported in the United States, from 22.9% in 1988 to 42.4% in 2018. Similar trends have been observed for pre-pregnancy obesity, leading to concerns about associated adverse maternal and neonatal outcomes. However, improved outcomes have been linked to regular physical activity during pregnancy.²

“Studies in the United States demonstrate that only 3%–15% of pregnant individuals meet these physical activity guidelines, with even lower rates observed in those with obesity compared to those without,” wrote investigators.¹ “Furthermore, data specific to pregnant individuals with class 3 obesity are limited.”

Survey details and physical activity categories

The retrospective cohort study was conducted to determine rates of meeting physical activity goals among pregnant patients and how these rates differ based on body mass index (BMI). Women aged at least 18 years with a singleton pregnancy and self-reporting physical activity from conception to 20-weeks’ gestation were included in the analysis.

Patients with missing pre-gravid BMI or not having a pregnancy lasting beyond 20 weeks’ gestation were excluded from the analysis. Intake surveys were used to obtain patient demographics, medical history, and social determinants of health.

Two questions about the number of days per week engaging in moderate to strenuous exercise and how many minutes on average patients participate in this activity were included in the survey. Categories of physical activity included under 150 minutes per week and at least 150 minutes per week.

The percentage of patients within each BMI category meeting the recommended physical activity guidelines was reported as the primary outcome. Meeting guidelines were defined as having at least 150 minutes per week of exercise. BMI categories included underweight, normal, overweight, obese class 1, obese class 2, and obese class 3.

Physical activity levels across BMI categories

There were 6884 participants included in the final analysis, 510 of whom were classified as having class 3 obesity. Maternal age did not significantly differ between groups but reduced gestational weight gain was reported in patients with increased BMI. Additionally, patients with higher BMI had earlier delivery and rates of large for gestational age.

Having at least 150 minutes of physical activity per week was reported in 34% of patients with a normal BMI. However, all other BMI categories except for underweight presented with reduced physical activity, leading to a greater proportion of patients failing to meet the recommended threshold.

Among patients with class 3 obesity, only 22% of those with a BMI of 40 to 49.9 kg/m² and 18% of those with a BMI of 50 kg/m² or greater reported at least 150 minutes of physical activity per week. Average durations of physical activity per week were 101.2 and 107.7 minutes, respectively, vs 126.5 minutes in patients with a normal BMI.

Implications

These results highlighted reduced levels of physical activity in pregnant patients, especially those with obesity. Investigators concluded these differences in physical activity may contribute to disparities in pregnancy outcomes.

“Future research should focus on developing and evaluating interventions that promote physical activity during pregnancy, as well as identifying barriers to participation,” wrote investigators.

References

1. Nguyen EM, Branda ME, Szymanski LM. Physical activity during pregnancy stratified by body mass index: A focus on class 3 obesity. Pregnancy. 2025. doi:10.1002/pmf2.70083
2. ACOG Committee Opinion No. 650: Physical activity and exercise during pregnancy and the postpartum period. Obstet Gynecol. 2015;126(6):e135-e142. doi:10.1097/AOG.0000000000001214