Abstract
Current ACOG guidelines recommend exercise during a low-risk pregnancy for 30 minutes on most, if not all days of the week. However, little is known about how the volume of exercise performed during pregnancy affects fetoplacental size. In addition, the confounding effects of maternal nutrient intake and weight gain, and how they interact with exercise volume to influence fetoplacental size have not been appropriately addressed. Therefore, the purpose of this study was to examine the effects of varying maternal exercise volumes on neonatal birthweight and placental volume, while addressing the influence of maternal nutrient intake and weight gain. Subjects evaluated for this study included pregnant women who walked during gestation (n=26), performed non-walking aerobic exercise during gestation (n=30), or remained as sedentary controls (n=32). At 16, 20, 24, 28, 32, 36 weeks gestation, women recorded their nutrient intake for 3 consecutive days. Additionally, they kept monthly exercise logs indicating the type and duration of their exercise. Nutrient variables calculated included average daily Calorie intake, average daily carbohydrate intake, average daily protein intake, average daily fat intake, and average daily fiber intake. Exercise volume was calculated as the average number of minutes per week spent performing exercise. Latent growth modeling was the statistical procedure used to analyze how change in maternal exercise volume and nutrient intake throughout gestation affects neonatal outcomes. Neonatal outcomes measured were birthweight, corrected birthweight for gestational age, sex, race, and socioeconomic status, and placental volume at delivery. Maternal walking volume had no effect on newborn birthweight or corrected birthweight, while it was inversely related to placental size at birth. Maternal non-walking aerobic exercise volume was inversely related with newborn birthweight, while there was a trend toward an inverse relationship with corrected birthweight and placental volume. Controlling for Calorie intake strengthened the relationship between any form of exercise volume and infant birthweight. Calorie intake, carbohydrate intake, and protein intake were all positively related to infant birthweight. Fiber intake was significantly inversely related to placental volume. Finally, maternal exercise volume and nutrient intake were not related to maternal weight gain. This data suggests that neonatal outcome will be affected by variations in exercise protocol. In addition, nutrient intake is a potentially confounding variable that should be examined when undertaking studies addressing the role of maternal exercise on neonatal outcome.