Clinical significance of normalization of uterine artery pulsatility index with maternal heart rate for the evaluation of uterine circulation in pregnancy-induced hypertension.

OBJECTIVE

To investigate whether the use of normalized pulsatility index (PI) improves evaluation of the fetal prognosis in pregnancy-induced hypertension (PIH).

METHOD

Eighty women with uncomplicated pregnancies and 46 women with PIH (33 with pre-eclampsia and 13 with gestational hypertension) were included in the study. Uterine artery PI and normalized PI were analyzed in relation to two neonatal parameters: incidence of small-for-gestational age infants and incidence of Cesarean section for non-reassuring fetal status.

RESULTS

In normal pregnancy, the normalized uterine artery PIs (mean +/- SD) at 25, 31, and 39 weeks of gestation were 0.70 +/- 0.15, 0.71 +/- 0.16, and 0.65 +/- 0.13, respectively. Using non-normalized PI, 10 of 46 PIH cases had increased PI; however, with normalization, two pre-eclampsia cases were added to the group with elevated PI, giving a total of 12. The incidences of small-for-gestational age infants and Cesarean section due to non-reassuring fetal status were higher in the elevated normalized uterine artery PI group. The use of normalized PI appeared to reduce the false-negative results in pre-eclampsia and PIH. After normalization, sensitivity, positive predictive value and negative predictive value of PI for small-for-gestational age infants and Cesarean section due to non-reassuring fetal status were improved in cases with pre-eclampsia and PIH. The incidence of these complications was low in gestational hypertension.

CONCLUSIONS

Normalization of the PI may improve predictive values for small-for-gestational age infants and delivery by cesarean section due to non-reassuring fetal status in PIH.