Abstract Body: Background: Adequate physical activity and limited sedentary time during pregnancy reduce the risk of pregnancy-related complications. This study examined associations between self-reported environmental support and device-measured physical activity (PA) and sedentary behavior across pregnancy, and whether these associations differed between rural and urban women in the Pregnancy 24/7 Multisite Cohort Study.

Methods: PA was measured by a thigh-worn activPAL each trimester. Participants completed an Environmental Support Survey at baseline and after any address change. Environmental support scores were categorized into tertiles (high, mid, low). Multivariable linear regression models examined associations between environmental support and PA, adjusted for pre-pregnancy BMI, socioeconomic status, age, and rurality. Rurality was formally tested as an effect measure modifier and confounder, in both crude and adjusted models.

Results: Compared to women reporting low-support environments, those with high-support engaged in 8.76 (p<0.001), 6.68 (p<0.001), and 5.86 (p=0.001) more minutes/day of moderate-to-vigorous PA (MVPA) and 820 (p=0.0.2), 663 (p=0.04), and 658 (p=0.01) more steps/day in trimesters 1, 2, and 3, respectively. Compared to low-support environments, women with mid-support engaged in 6.31 (p<0.001) and 4.44 (p=0.003) more minutes/day of MVPA in trimesters 2 and 3 and 697 (p=0.01) more steps/day in trimester 3. Environmental support level was not associated with sedentary time or light physical activity. Associations between environmental support and PA were similar in urban and rural areas.

Conclusions: Findings underscore the role of supportive environments in fostering physical activity during pregnancy. Future studies using GIS-based environmental measures may reduce bias from self-reported environmental assessment.