Uterine and umbilical flow velocity waveforms in the supine hypotensive syndrome.

Changes in central hemodynamics and uterine and umbilical artery flow velocity waveforms were studied in ten healthy women 33-41 weeks pregnant who had signs of the supine hypotensive syndrome. When changing the position from left lateral recumbency to supine, there was an initial increase in mean arterial pressure (MAP) of 13% and in maternal heart rate of 30%. After this, the MAP decreased by 19% and, simultaneously, a 26% increase (P = .002) in uterine artery systolic/diastolic (S/D) ratio was recorded. When the changes in MAP and in the uterine artery S/D ratio were compared, the response was slower and recovery faster in the uterine circulation. Two patients evidenced a transient deceleration in the fetal heart rate and a simultaneous increase in the umbilical artery S/D ratio.