The U-Shaped Relationship Between Pregnancy Physical Activity and Neonatal Birth Weight

Abstract This study prospectively analyzed the relationship between physical activity during pregnancy and neonatal birth weight in 337 singleton pregnant women in Shenzhen, China. The participants were enrolled from May to October 2023 at the Shenzhen Second People's Hospital, where they underwent routine prenatal check-ups and deliveries. The physical activity during pregnancy was assessed three times using the Pregnancy Physical Activity Questionnaire (PPAQ) at three different stages: mid-pregnancy (T1), late pregnancy (T2, preterm), and late pregnancy (T3, full-term).After adjusting for confounding factors using generalized additive models (GAM) and smooth curve fitting, a U-shaped relationship was observed between physical activity during pregnancy and neonatal birth weight. When physical activity exceeded 218.22 MET-h•wk⁻ ¹, each standard deviation increase in physical activity was associated with a 544.04g increase in birth weight (β: 544.04, 95% CI: 184.77 to 903.32, P = 0.0032). No significant association was found below this threshold. The results suggest that moderate to higher levels of physical activity during late pregnancy are beneficial for fetal weight gain, whereas both low and excessively high levels may be detrimental. Clinically, individualized and balanced physical activity prescriptions during pregnancy should be developed.