Umbilical artery flow velocity waveforms following maternal exercise.

The effect of acute exercise on pregnant women in the last trimester of pregnancy and the changes in fetal umbilical artery flow velocity waveforms were studied. One hundred and forty-three healthy pregnant women underwent an acute exercise test. The exercise was performed on an upright bicycle ergometer for 5 minutes, followed by 30 minutes of recovery. The baseline control values of umbilical artery velocity waveforms were compared with those after exercise. The mean exercise intensity achieved was 67.4% (55-90%) of submaximal exercise. Maternal heart rate rose significantly from a mean of 89 (68-120) beats per minute at rest to a mean of 144 (116-200) beats per minute after exercise (P<0.001). Maternal blood pressure rose significantly after exercise from a mean systolic of 112 (80-150) mmHg to a mean of 147 (120-200) mmHg (P<0.001), and from a mean diastolic of 67 (40-85) mmHg to a mean of 84 (70-100) mm Hg (P<0.001). The mean fetal umbilical pulsatility index (PI) was shown to decrease significantly following exercise at 2 and 4 minutes of recovery. It is concluded that (1) an acute exercise test of this intensity causes a significant decrease in PI index after 2 and 4 minutes of recovery; (2) an exercise intensity between 55 and 75% causes a decrease in the PI after exercise while exercise of 76-90% of submaximal exercise causes a rebound increase after an initial decrease at 2 minutes; (3) it may be possible to use this pattern of exercise as an exercise test to differentiate between low- and high-risk pregnancies. Studies on high-risk pregnancies are being prepared for publication.