Comparative Study of Abdominal Versus Transvaginal Ultrasound for Uterine Artery Doppler Velocimetry at 11 to 13 Weeks

Objectives-To compare the first-trimester uterine artery pulsatility index (PI) measured by abdominal and transvaginal ultrasound (US). Methods-We performed a prospective study of singleton pregnant women recruited at 11 to 13 weeks' gestation. The mean uterine artery PI was obtained by abdominal followed by transvaginal US. The mean of the left and right uterine artery PIs was used, and differences between approaches were computed. The intraclass correlation coefficient and a Bland-Altman plot were used to compare the two approaches. Results-Data were available for 940 participants, including 928 (99%) with uterine artery PIs obtained on both uterine sides. The mean uterine artery PI decreased with gestational age in both approaches (P < .001). We observed a moderate correlation between abdominal and transvaginal mean uterine artery PIs (intraclass correlation coefficient, 0.72; 95% confidence interval, 0.69 to 0.75). Values obtained by abdominal US (median, 1.70, interquartile range, 1.35 to 2.09) were greater than those obtained by transvaginal US (median, 1.65; interquartile range, 1.37 to 1.99). There was a significant increase in differences as average measurements became higher (P < .01). Conclusions-The first-trimester mean uterine artery PI decreases with gestational age in both approaches. Abdominal US could be associated with greater uterine artery PI values than transvaginal US, especially at higher measurements. The first-trimester uterine artery PI for prediction of adverse perinatal outcomes should be adjusted for gestational age and possibly for the US approach.