Physical exercise during pregnancy and fetal growth measures: a study within the Danish National Birth Cohort.

OBJECTIVE: The objective of the study was to examine the association between physical exercise during pregnancy and fetal growth measures. STUDY DESIGN: Data on 79,692 liveborn singletons from the Danish National Birth Cohort were collected between 1996 and 2002. Mean differences in birthweight, length, ponderal index, head and abdominal circumference, and placental weight and hazard ratios of small-and large-for-gestational-age babies were calculated. RESULTS: Our data indicated smaller babies in exercising women compared with nonexercisers, but the differences were small, and only a few were statistically significant. Exercising women had a slightly decreased risk of having a child small for gestational age (hazard ratio, 0.87; 95% confidence interval, 0.83-0.92) and large for gestational age (hazard ratio, 0.93; 95% confidence interval, 0.89-0.98). CONCLUSION: The findings do not indicate sizable effects on fetal growth measures related to exercise apart from a modest decreased risk of small- and large-for-gestational-age infants. These findings do not speak against advising pregnant women to be physically active during pregnancy.