Associations between physical activity, sedentary behavior, body mass index and changes in placental structure and vascularization - data from the FitMum randomized controlled trial.

OBJECTIVE

Maternal physical activity (PA), sedentary time (ST) and body-mass index (BMI) might influence placental development. We examined associations between PA, ST during pregnancy and pre-pregnancy BMI, and placental structural outcomes as well as mRNA expression levels of vascular growth factors.

METHODS

The FitMum randomized controlled trial included 220 healthy, pregnant women. PA and ST were objectively measured 24/7 from inclusion before gestational week 15 + 0 until delivery. This secondary analysis of FitMum includes all participants with an available placenta sample (n = 118). Placental sections were stained with immunofluorescence and H&E. Villous density as well as vessel area were assessed with Visiopharm software. Placental samples with sufficient quality (n = 107) were bulk RNA-sequenced and genes relevant for placental vascularization were selected for analysis. Associations of moderate-to-vigorous intensity PA (MVPA), ST and pre-pregnancy BMI, with villous density, vessel surface area, placental weight, and mRNA-counts, were analyzed with multiple regressions.

RESULTS

Increased MVPA was associated with increased placental weight (p = 0.005), while higher pre-pregnancy BMI was associated with lower area of medium-sized and large blood vessels in the placenta (p = 0.002). No associations were observed between MVPA or ST and histologic outcomes or mRNA expression levels.

CONCLUSION

PA during pregnancy was not associated with vessel per villous area or villous density nor mRNA expression levels of vascular growth factors, but with increased placental weight. High pre-pregnancy BMI was associated with lower area of medium-sized and large blood vessels in the placenta, suggesting metabolic status before pregnancy may play a key role in placental vascular development.