Exercise in pregnant women and birth weight: a randomized controlled trial

Background: Birth weight plays an important role in infant mortality and morbidity, childhood development, and adult health. To date there are contradictory results regarding the role of physical activity on birth weight. In addition, it is questioned whether exercise during second and third trimesters of pregnancy might affect gestational age and increase the risk of preterm delivery. Hence, the purpose of this study was to examine the effect of a supervised exercise-program on birth weight, gestational age at delivery and Apgar-score. Methods: Sedentary, nulliparous pregnant women (N = 105), mean age 30.7 +/- 4.0 years, pre-pregnancy BMI 23.8 +/- 4.3 were randomized to either an exercise group (EG, n = 52) or a control group (CG, n = 53). The exercise program consisted of supervised aerobic dance and strength training for 60 minutes, twice per week for a minimum of 12 weeks, with an additional 30 minutes of self-imposed physical activity on the non-supervised week-days. Results: There was no statistically significant difference between groups in mean birth weight, low birth weight (< 2500 g) or macrosomia (= 4000 g). Per protocol analyses showed higher Apgar score (1 min) in the EG compared with the CG (p = 0.02). No difference was seen in length of gestation. Conclusion: Aerobic-dance exercise was not associated with reduction in birth weight, preterm birth rate or neonatal well-being.