Sensitivity of higher, lower and mean second‐trimester uterine artery Doppler resistance indices in screening for pre‐eclampsia

OBJECTIVES: First-trimester Doppler studies have reported that the lower uterine artery (UtA) resistance index (RI) is better for the prediction of pre-eclampsia (PE) than is either the mean or higher indices. The aim of this study was to determine if this relationship is true in the second trimester. METHODS: This was a retrospective study of 24 859 singleton pregnancies. During the study period second-trimester UtA Doppler assessment was routinely available to all nulliparous women and to parous women at increased risk of PE. UtA-RI was obtained at the time of the anomaly scan. Receiver-operating characteristics curves for the lower, mean and higher UtA-RI for the prediction of PE were calculated. RESULTS: There were 1037 cases of PE. There were significant associations between UtA-RI and PE, the association being stronger for early and preterm than late or term PE. There was no significant difference in the strength of the association between lower, mean and higher RI with PE at any gestation. CONCLUSION: Performance of UtA-RI in predicting PE is no different for the lower, higher or mean RI of the two UtAs. The most likely explanation for the discrepancy with first-trimester studies is that the placental-side effect on Doppler indices may change with advancing gestational age and progressive trophoblast development and invasion.