Reference range for uterine artery Doppler pulsatility index using transvaginal ultrasound at 20-24w6d of gestation in a low-risk Brazilian population.

Objective: To establish reference range for uterine artery (UtA) Doppler pulsatility index (PI) using transvaginal ultrasound at 20-24w6d of gestation in a Brazilian population.

Material And Methods: A retrospective cross-sectional study in 847 low-risk pregnant women undergoing routine second trimester ultrasound examination was conducted from February 2012 through March 2015. The mean UtA PI was calculated using color Doppler ultrasound with UtA gated at the level of the internal os.