Exercise during pregnancy: effects on the fetus.

Two studies concerning the effects of running during pregnancy were conducted. In the first study observations involved both retrospective and longitudinal obstetric and neonatal evaluation of 33 runners and 11 non-runner control subjects. The results indicated no significant differences between the two groups with regard to maternal weight gain and neonatal delivery weight. There were less quantitative complications of labor and delivery for the runners, but qualitatively there may be a trend toward failure to progress and resultant cesarean section. The second study involved simultaneous electronic monitoring of maternal and fetal heart rate patterns during exercise. In the three technically distinct tracings obtained there was a transient fetal bradycardia during a treadmill testing experience. It was also observed that the fetal heart rate returned to normal during the period of exercise suggesting that the observed deceleration pattern is reversible. Etiology of the bradycardia remains enigmatic.