This study was conducted to determine the impact of maternal exercise on fetal breathing and fetal body movement, which are commonly used for assessing fetal well-being. Twelve healthy patients with a range of gestational ages of 26 to 36 weeks, who actively exercised throughout pregnancy, participated in the study. The patients walked on a motorized treadmill using a modified Bruce protocol until the maternal heart rate reached 75% of the age-predicted maximal heart rate. Fetal activities (fetal breathing and fetal body movement) were continuously monitored with real-time ultrasonography for 20 minutes before and after the standardized exercise test. Our results demonstrate that there is a significant increase in maternal heart rate and blood pressure associated with exercise. In addition, there is a significant decrease in the total duration and frequency of fetal breathing and fetal body movements following acute maternal exercise.