Maternal physical activity and sitting time and its association with placental morphology and blood flow during gestation: findings from the Queensland family cohort study

Objectives Exercise during pregnancy is associated with placental morphological alterations, however research in this area is limited. Given the emphasis on the beneficial effects of antenatal exercise, it is important to understand the effect of physical activity (PA) on placental function and its relationship to fetal growth and development. The aim of this study was to investigate the association between PA, sitting time, and placental outcomes measured during gestation. Design Prospective cohort study. Method Pregnant women in the Queensland Family Cohort study self-reported PA at 24 and 36 weeks of gestation using a modified version of the Active Australia Survey (n = 203). Participants were categorised into PA volume groups of nil-low (0- < 500 MET.minutes/week), moderate (500- < 1000 MET.minutes/week), or high-volume activity (≥1000 MET.minutes/week). Participants also reported average daily sitting time, whereby excessive sitting time was considered as ≥8 h/day. Placental stiffness, thickness, and uteroplacental blood flow resistance were measured by ultrasound imaging at each timepoint. Results PA volume was not associated with changes to placental morphometrics or uteroplacental blood flow resistance at 24 or 36 weeks of gestation. Excessive sitting time at 36 weeks of gestation was associated with greater placental stiffness (p = 0.046), and a lower umbilical artery pulsatility index (p = 0.001). Conclusions Placental tissue stiffness and umbilical artery resistance were altered in late gestation with higher maternal sitting time but not with PA volume. Overall, excessive sitting time may be a risk for suboptimal placental function and could be an important focus for antenatal care.