Abstract Body: Background: At least 150 minutes/week of moderate intensity physical activity is recommended during pregnancy, yet pregnancy presents barriers to achieving these guidelines. Some data suggest that activities such as standing, daily steps, and breaking up sedentary behavior may also improve pregnancy health. We aimed to describe and compare typical patterns of these lighter intensity behaviors across pregnancy in a large cohort of pregnant women using gold standard, device-based measures.

Methods: Pregnancy 24/7 is an ongoing multi-site cohort study in 500 pregnant participants conducted at the University of Iowa, University of Pittsburgh, and West Virginia University. The study’s primary objective is to identify optimal 24-h behavior compositions associated with the lowest risk of hypertensive disorders of pregnancy and other adverse pregnancy outcomes. Herein, we describe patterns of lower-intensity behaviors across trimesters. Participants aged 18-45 years, not on medications for blood pressure or diabetes, and without physical or medical conditions that severely impact 24-h behaviors, were recruited in the first trimester. They were instructed to wear a thigh-worn activPAL3 micro for 24-h x 7 full days and complete a concurrent wear diary during each trimester of pregnancy. Accelerometer data were processed by PALTechnologies software and a customized R program that quantified average daily standing (h/day), steps, sit-stand transitions, and prolonged sedentary behavior accumulated in 30-min or 60-min bouts (h/day) each trimester. Linear mixed models compared accelerometer outcomes across trimesters of pregnancy.

Results: Participants (n=474) with valid accelerometer data for least one visit (to date) had an average age of 30.8 years and 84% reported Non-Hispanic White race/ethnicity. Sedentary behavior and lighter-intensity activities all differed across trimesters (p≤0.002, see Table), with optimal patterns in the second trimester. Pregnant women were least likely to engage in standing and break up prolonged sedentary behavior (lower sit-stand transitions and higher sedentary behavior in bouts) in the first trimester, while steps were lower by ~500 steps per day in the third trimester.

Conclusions: Sedentary behaviors, standing, and daily steps vary differentially across pregnancy. These patterns, along with how these behaviors associate adverse pregnancy outcomes, will guide the design of comprehensive activity interventions to promote pregnancy health.