Doppler measurements on branches of the uterine artery in normal, hypertensive and growth-retarded pregnancies.

The quality and reliability of pulsed Doppler recordings from branches of the uterine artery were tested by studying 37 normotensive pregnancies and 14 complicated by pregnancy-induced hypertension (PIH) lasting for several minutes. The coefficients of variation of mean velocity and A/B ratio (= peak systolic/end diastolic velocity) were 0.06 and 0.08, respectively. Thus, calculations of A/B ratio from a limited number of heart beats should be reliable. Calculations were then made from uterine artery Doppler recordings in 65 normotensive pregnancies and 32 with PIH. A significantly higher A/B ratio was found in the PIH group. Among the normotensives, no statistically significant difference in A/B ratio was found between those who gave birth to appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA: less than 10th centile) infants. In the PIH group a significant difference was found; A/B: 1.95 versus 1.78 in the SGA and AGA groups, respectively. The latter was still significantly higher than the normotensive (= 1.60). Two PIH subgroups with equivalent blood pressures and proteinuria, but who gave birth to AGA or SGA infants, were compared. A/B ratio from the latter was significantly higher. These findings show that PIH is associated with increased uteroplacental vascular resistance; increased vascular pathology is associated with fetal growth retardation.