Do heart rate and velocity variability derived from umbilical artery velocity waveforms change prior to clinical pregnancy-induced hypertension?

Objective To investigate the hypothesis that alterations in heart rate vari ability peak systolic velocity variability and time-averaged velocity varia bility in the human umbilical artery may predict early signs of dysfunction al fetat - placental coupling in pregnancies that later develop pregnancy-i nduced hypertension. Methods Doppler flow velocity recordings from the umbilical artery were per formed at 10-20 weeks of gestation in 12 nulliparous women who subsequently developed pregnancy-induced hypertension. From umbilical artery velocity w aveforms of at least 12 s in duration we determined absolute values and bea t-to-bear variability in fetal heart rate, peak systolic and time-averaged velocity and compared these findings with those in normal nulliparous pregn ant women matched for gestational age. Results Absolute values for fetal heart rate, peak systolic and time-averag ed velocity as well as beat-to-beat variability in fetal heart rate did not differ significantly between women later developing pregnancy-induced hype rtension and normal controls. However, variability in peak systolic velocit y and time-averaged velocity were decreased in women who subsequently devel oped pregnancy-induced hypertension. Conclusions Whereas fetal heart rate variability was similar, umbilical art ery flow velocity variability was reduced in women developing pregnancy-ind uced hypertension compared with controls. It is proposed from this study th at variability of the umbilical artery flow velocity is associated with mec hanical changes in the vascular bed of women who Inter develop pregnancy-in duced hypertension.