Uterine artery pulsatility index at 30-34 weeks' gestation in the prediction of adverse perinatal outcome

Objective: To investigate the potential value of uterine artery Doppler at 30 34 weeks’ gestation in the prediction of adverse perinatal outcome.

Methods: Screening study in 30,780 singleton pregnancies at 30 34 weeks. Uterine artery pulsatility index (PI) was measured and the values were converted to multiples of the median (MoM) after adjustment from variables in maternal characteristics and medical history that affect the measurements. Multivariable logistic regression analysis was used to determine if uterine artery PI had a significant additional contribution to maternal characteristics, medical history and obstetric factors in predicting adverse outcome. The detection rate (DR) and false positive rate (FPR) of screening by uterine artery PI were estimated for stillbirth, cesarean section for fetal distress, umbilical arter ial cord blood pH <7.0 or umbilical venous pH <7.1 and Apgar score <7 at 5 minutes.

Results: The incidence of adverse perinatal outcome was higher in small for gestational age (SGA) than in non SGA fetuses, but the majority of cases for each adverse outcome were in the non SGA group, including about 70% of stillbirths and more than 80% of cases of cesarean section for fetal distress, low cord blood pH and low Apgar score. The performance of uterine artery PI >95 th percentile in screening for each adverse outcome was poor with DR of 6 16% and FPR of 5 6%. T he DR of high uterine artery PI for adverse outcome was higher in the SGA than non SGA groups, including 24% vs. 13% for stillbirth , 15% vs. 5% for cesarean section for fetal distress, 22% vs. 9% for low cord blood pH and 20% vs. 3% for low Apgar score.

Conclusion: High uterine artery PI at 30 34 weeks’ gestation may be useful in the prediction of adverse perinatal outcome in pregnancies with SGA fetuses, but not in those with non SGA fetuses.