Sedentary Behavior Across Pregnancy, Gestational Age at Delivery, and Birthweight

Abstract

PURPOSE: Lower gestational age at delivery (GAD) and large for gestational age birthweight (LGA) are indicators of poorer maternal-fetal health. While physical activity during pregnancy has been associated with greater GAD and lower risk of LGA, the effects of sedentary behavior (SB) on these outcomes are unknown. We aimed to describe patterns of SB across pregnancy and associations with GAD and risk for LGA METHODS: In this cohort study, SB (activPAL micro3) and physical activity (waist-worn ActiGraph GT3X-BT) were assessed in women for ≥ 4 days with > 10 hours, in each trimester of pregnancy. This preliminary analysis (59% recruited) includes women with available birth records and valid activity data for >1 trimester (n=56). Birthweight (BW) and GAD were abstracted from medical records. BW was categorized as LGA if > 90th percentile (n=18, 31%). Mean (SD) percent time spent sedentary was calculated in each trimester and differences across trimesters were tested using linear mixed models. The association of SB with continuous GAD and odds of LGA were estimated in separate regression models for each trimester. All beta coefficients were standardized (std β) per SD and adjusted for pre-pregnancy body mass index. If SB was associated with outcomes, further models estimated the effect of replacing SB with light physical activity (LPA) or moderate to vigorous physical activity (MVPA). RESULTS: Women spent a high percentage of time sedentary across trimesters: 1st (n=53) 64.0% (10.9); 2nd (n=50) 63.5% (9.5); and 3rd (n=47) 63.8% (10.4). SB did not differ across trimesters (p=0.792). Higher percent time spent sedentary in the first trimester was associated with lower GAD (std β=-0.45, p=0.038). Replacing first trimester SB with LPA (std β=0.48, p=0.037), but not MVPA (std β =-0.12, p=0.581), was associated with greater GAD. SB was not significantly associated with GAD in the 2nd (std β =-0.24, p=0.241) or 3rd (std β =-0.22, p=0.264) trimester. Odds of LGA was not significantly associated with SB in the 1st (OR=0.75, p=0.389), 2nd (OR=0.80, p=0.503), or 3rd (OR=1.03, p=0.932) trimester. CONCLUSIONS: Women in this study were highly and consistently sedentary across pregnancy. Higher LPA and lower SB during the first trimester may be advantageous for greater GAD, though risk for LGA offspring did not appear to be associated with SB.