The mediating role of placenta in the relationship between maternal exercise during pregnancy and full-term low birth weight

Objective: To explore the association of maternal exercise during pregnancy with full-term low birth weight (FT-LBW) and whether placenta mediates their association.

Study design: We investigated 326 pregnant women delivering FT-LBW weight newborns (cases) and 1644 delivering full-term normal birth weight newborns (controls) in this case-control study. Information concerning maternal exercise during pregnancy, socio-demographics and obstetric characteristics were collected at Women and Children's Hospitals of Shenzhen and Foshan in Guangdong, China.

Results: After adjusting for the potential confounders, maternal exercise frequency and duration during pregnancy were significantly negatively associated with FT-LBW, respectively. Moreover, compared with mothers taking no exercise during pregnancy, those taking exercises were significantly negatively associated with FT-LBW except those taking low/medium frequency and short duration exercise and high-frequency and long duration exercise, and their adjusted ORs ranged from 0.30 to 0.62. Furthermore, mediation analysis illustrated that placental weight partially mediated 27.20% of the association between maternal exercise frequency during pregnancy and FT-LBW, but not the association between maternal exercise duration during pregnancy and FT-LBW.

Conclusions: Maternal exercise during pregnancy is beneficial for lowering FT-LBW risk, especially when taking appropriate and enough exercise. Placenta weight partially mediates the association between maternal exercise frequency during pregnancy and FT-LBW.