Placental pulsatility index: a new, more sensitive parameter for predicting adverse outcome in pregnancies suspected of fetal growth restriction

IntroductionThe pulsatility indices of the umbilical and uterine arteries are used as the surrogate measures of utero-placental perfusion. Combining the two might simplify the evaluation of total placental vascular impedance, possibly improve prediction of adverse outcomes, and help identify pregnancies with suspected fetal growth restriction that need more intense surveillance. Material and methodsUmbilical and uterine blood flow velocities were recorded using pulsed-wave Doppler in a longitudinal study of 53 low-risk pregnancies (248 observations) during 20-40weeks of gestation. Pulsatility indices was calculated for each of these vessels. A new placental pulsatility index was constructed as: (umbilical artery pulsatility index + mean of the left and right uterine artery pulsatility indices)/2, and mean +2SD defined as abnormal. Gestational age-specific reference percentiles were calculated for the second half of pregnancy and related to values obtained from 340 pregnancies with suspected intra-uterine growth restriction to test its ability to predict adverse pregnancy outcome. ResultsThe placental pulsatility index was closely associated with gestational age and decreased with advancing gestation in normal pregnancy. The placental pulsatility index had a higher sensitivity and comparable specificity in predicting adverse outcome in pregnancies suspected of intra-uterine fetal growth restriction when compared with conventional umbilical and uterine artery pulsatility indices. ConclusionsThe new placental pulsatility index, reflecting placental vascular impedance on both the fetal and maternal side of placenta, improves prediction of adverse outcome in pregnancies suspected of intra-uterine fetal growth restriction.