Stroke and minute distance in pregnancy: a longitudinal study using Doppler ultrasound

Using Doppler ultrasound directed at the aortic arch, stroke and minute distance were measured in 45 normal singleton pregnancies and compared with 42 controls. In the non-pregnant controls, stroke distance was 5% more in the supine than in the left lateral position (P less than 0.01) and during pregnancy this relativity was maintained until 36 weeks gestation. In the supine and left lateral positions respectively, stroke distance was increased by 8% (both) at 4 weeks (P less than 0.05 and NS), by 14 and 11% at 8 weeks (P less than 0.001 and P less than 0.01) and showed a maximum increase of 21 and 20% at 16 weeks gestation (both P less than 0.001). At 40 weeks, supine stroke distance was 14% less than the non-pregnant control value (P less than 0.001), and 6% less than the value in the left lateral position (P less than 0.05), which was itself not significantly different from that in the non-pregnant controls. The maximum increase of heart rate was at 32 weeks, by 24% in the supine and by 19% in the left lateral position (both P less than 0.001). Minute distance was maximally increased by 37% in the supine at 16 weeks (P less than 0.001) and by 30% in the left lateral position at 24 weeks (P less than 0.001). Thereafter, minute distance, measured in both positions, declined until at 40 weeks it was not significantly different from the non-pregnant control value.