Evaluating the Optimal Definition of Abnormal First-Trimester Uterine Artery Doppler Parameters to Predict Adverse Pregnancy Outcomes.

OBJECTIVES To investigate the optimal definition of abnormal first-trimester uterine artery Doppler parameters associated with adverse pregnancy outcomes. METHODS A prospective cohort of women with singleton gestations between 11 and 14 weeks consented to uterine artery Doppler measurements. Doppler parameters were measured bilaterally, and mean pulsatility index (PI) and resistive index (RI) values were calculated. The presence of notching was also determined. Each parameter was evaluated for prediction of preeclampsia, early preeclampsia (<34 weeks), preterm birth (<37 weeks), early preterm birth (<34 weeks), and small for gestational age (SGA; birth weight <10th percentile). Descriptive statistics evaluated the association between abnormal Doppler indices and outcomes. A receiver operating characteristic (ROC) analysis was used to define the best cutoff points for mean PI and RI. The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were calculated for bilateral notching and mean PI and RI percentiles. RESULTS Of 1192 patients with complete outcome data, preeclampsia was seen in 8.4%, early preeclampsia in 1.8%, preterm birth in 12.9%, early preterm birth in 5.6%, and SGA in 8.5%. A mean PI above the 75th percentile (>1.91) was the best index for predicting early preeclampsia (sensitivity, 45.0%; specificity, 75.5%; NPV, 98.7%; ROC area, 0.65). A mean PI above the 75th percentile was also the best index for predictive early preterm birth (sensitivity, 40.0%; specificity, 76.0%; NPV, 95.5%; ROC area, 0.65). None of the parameters were significant for predicting SGA. CONCLUSIONS A mean uterine PI above the 75th percentile is the most discriminative abnormal uterine artery Doppler parameter for predicting both early preeclampsia and early preterm birth.