The effect of maternal exercise on uterine artery velocimetry waveforms

One hundred and two subjects in the second half of pregnancy were subject to an acute exercise test lasting 5 minutes on an upright bicycle ergometer. The pulsatility index (using Doppler ultrasound) of the right uterine artery was analysed before exercise and at 2, 4, 6, 8, 10, 12, 16, 20, 24 and 30 minutes after exercise. The mean exercise intensity achieved was 67.2% of sub-maximal exercise (range 51-90%). At 2 minutes post-exercise, the mean uterine artery pulsatility index was increased from the baseline value, reaching a maximum of 0.64 at 8 minutes (baseline 0.583). After 8 minutes there was a gradual decrease in the pulsatility index, and at 24 and 30 minutes the values were significantly lower (P < 0.001 and P < 0.001 respectively). Smokers had significantly higher pulsatility index values than non-smokers (P < 0.004). Primigravidae also had lower resistance indices compared with multigravidae (P < 0.001). We conclude that exercise in the second half of pregnancy appears to cause a transient increase in the maternal uterine artery pulsatility index. We also believe that at this level of exercise intensity there was no evidence of harmful effects on maternal uterine blood flow.