[Changes in arterial uterine blood flow velocity waveform during uterine contraction and relaxation in labor]

The arterial uterine blood flow velocity waveform during uterine contraction and relaxation in labor was measured with ultrasonic continuous wave (CW) Doppler device in 44 pregnant women at 37-41 weeks of gestation. The fetal heart rate (FHR) was also recorded by cardiotocogram during labor in every case. 1. Both the resistance index (RI) and pulsatility index (PI) of the arterial uterine blood flow velocity waveform were significantly higher during uterine contraction than during relaxation (p less than 0.005). These increases in RI and PI during contraction were not influenced by the maternal heart rate. The reverse or interrupted end-diastolic flow was demonstrated in 16.3% of the cases. 2. No abnormal FHR patterns were observed in any of the cases except two with early deceleration or mild variable deceleration in which uterine arterial end-diastolic flow was maintained. The fetal conditions did not seem to be influenced by the reduction of arterial uterine blood flow in our study.