Maternal physical activity prior to and during pregnancy does not moderate the relationship between maternal body...

Maternal body mass index (BMI) is a significant determinant of infant macrosomia. Given the strong metabolic effects of physical activity (PA), independent of body mass, it is unclear as to whether maternal PA may affect the risk of delivering a macrosomic infant. Thus, the purpose of this study was to determine if maternal PA moderates the relationship between maternal BMI and infant macrosomia.

Cross-sectional study using data from the National Maternal and Infant Health Survey (1988).

Women with singleton pregnancies, delivering term (37-44 weeks), live-birth infants (n=6390) were included in the analyses. Multiple logistic regression models were performed to determine the moderating effects of maternal self-reported PA in the preconception and prenatal periods on the risk of infant macrosomia after adjusting for maternal age, race/ethnicity, gestational age and weight gain, smoking and alcohol use, and infant sex.

Mothers were on average 25 years of age and nearly 25% were overweight or obese. Prevalence of macrosomia was 9%. Overweight or obese women had increased odds of delivering a macrosomic infant (OR=1.69, p<0.0001; OR=1.67, p=0.0032, respectively). Nearly 50% and 42% of mothers reported participating in at least 30min of moderate PA, three times per week in the preconception and prenatal periods, respectively. Neither maternal PA in the preconception (OR=0.98, p=0.34) nor prenatal (OR=1.00, p=0.13) periods moderated the association between maternal BMI and infant macrosomia.

Maternal BMI was a significant predictor of infant macrosomia. However, mothers participating in at least 90min of PA per week in the preconception or prenatal periods did not moderate this association. More rigorous study designs and precise measurements of maternal PA and neonatal size are warranted.