Trimester-specific association between fetal growth and physical activity in pregnant women: total physical activity vs moderate-to-vigorous exercise

Objective To investigate the trimester-specific associations between maternal total physical activity level vs moderate-to-vigorous exercise and fetal growth disorders. Methods We analyzed 2062 mother-neonate pairs participating in the longitudinal China Medical University Birth Cohort Study. The Pregnancy Physical Activity Questionnaire was used to assess the physical activity level of women during the three trimesters. A higher level of total physical activity was defined as meeting or exceeding the cohort-specific 75th percentile, and a higher level of exercise was defined according to the Physical Activity Guidelines for Americans. Fetal growth disorder was defined as small-for-gestational age (SGA) or large-for-gestational age (LGA) at birth. Results Of the neonates included in this study, 7.1% were SGA and 15.5% were LGA. A higher level of total physical activity during the first trimester (adjusted relative risk (aRR), 0.62 (95% CI, 0.42-0.91)) and second trimester (aRR, 0.62 (95% CI, 0.41-0.95)) was associated with a lower risk of SGA, and a higher level of total physical activity during the third trimester was associated with a lower risk of LGA (aRR, 0.73 (95% CI, 0.54-0.97)). When analyzing physical activity by subtype, a higher level of occupational physical activity during the first and second trimesters was associated negatively with SGA risk, and higher levels of occupational and low-intensity physical activity during the first trimester were associated negatively with LGA risk. No significant association was found between maternal adherence to the Physical Activity Guidelines for Americans and risk of fetal growth disorders. Conclusions A higher total physical activity level during the first and second trimesters was associated with a decreased risk of SGA, whereas a higher total physical activity level in the third trimester was associated with a decreased risk of LGA. Pregnant women should be advised to increase their total physical activity levels instead of focusing on engaging in only moderate-to-vigorous exercise. (c) 2024 International Society of Ultrasound in Obstetrics and Gynecology.