FLOW VELOCITY WAVE-FORMS IN UTERINE AND UMBILICAL ARTERIES DURING SUBMAXIMAL BICYCLE EXERCISE IN NORMAL-PREGNANCY

Eight healthy women who were not conditioned athletes, at 35-38 weeks' gestation, performed a submaximal bicycle exercise test three times f or 4 minutes each with stepwise increases (73 +/- 27, 114 +/- 29, and 161 +/- 16 W) of the work load. The target heart rate at the end of th e last load was 170 beats per minute. The systolic-diastolic ratios (S /Ds) of flow velocity waveforms were measured with pulsed color Dopple r ultrasound in the uterine and umbilical arteries immediately after e ach work load and during recovery. The heart rates at the end of each load (133 +/- 3, 156 +/- 3, and 173 +/- 7 beats per minute) correspond ed to an average of 70, 83, and 92% of the calculated maximum heart ra te. With the subject in the sitting position on the ergometer before e xercise, the S/D in the uterine artery was 1.49 +/- 0.09, increasing g radually and significantly during the exercise to the maximum of 2.04 +/- 0.06 at 1 minute of recovery. Heart rate and S/D in the uterine ar tery correlated significantly (r = 0.58, P < .01). Although the mean a rterial pressure increased significantly during exercise from 92 +/- 6 to 109 +/- 10 mmHg, the significant decrease of the ratio of the mean arterial blood pressure and S/D suggests that the flow in the main ut erine artery may decrease during intense exercise. No changes occurred in the S/D of the umbilical artery flow velocity, but the fetal heart rate increased significantly.