Objective  To explore the influence of maternal physical activity during mid-pregnancy on infants′ intelligence development and to provide theoretical evidences for promoting maternal and infant health.

  Methods  Using prospective cohort study design, we recruited 392 singleton pregnant women having routine antenatal examination at Tongling Maternal and Child Health Hospital and followed them up to delivery from May 2014 to May 2015; we collected relevant data with a questionnaire interview and information on physical activity in middle stage of pregnancy using a scale developed by Danish researchers. We also performed a one-year follow up survey among 392 infants (172 males and 220 females) of the women from May 2015 to May 2016. We collected the infants′ information on feeding using a self-designed questionnaire and on mental development at age of 12-month with Chinese Revision of Bayley Scale of Infant Development (BSID-CR). The effects of maternal physical activity on the infants′ intelligence and physical development were analyzed with stepwise multivariate linear regression.

  Results  The average mental developmental index (MDI) and psycho-motorial developmental index (PDI) were 126.39 ± 13.61 and 113.61 ± 14.30 for all the infants; the MDI of the female infants was significantly higher than that of male infants (P < 0.05); while the PDI of the infants did not differ significantly by gender (P > 0.05). Moderate maternal physical activity during mid-pregnancy of the pregnant women was reversely correlated with the infants MDI (β = – 0.15, P = 0.013); whereas slight physical activity is positively correlated with infants′ PDI (β = 0.12, P = 0.048).

  Conclusion  For the women during mid-pregnancy, slight physical activity is positively correlated with their infants′ psycho-motorial developmental index but moderate physical activity is reversely correlated with the infants′ mental developmental index at age of 12-month. The results suggest that pregnant women should maintain appropriate physical activity.