The effect of prenatally administered vaginal progesterone on uterine artery Doppler in asymptomatic twin pregnancies.

OBJECTIVES: This study investigated the influence of vaginal progesterone on uterine circulation in asymptomatic twin gestations. STUDY DESIGN: This study was a secondary analysis of a randomized, double-blind, placebo-controlled trial of twin pregnancies exposed to vaginal progesterone or placebo. We included all trial participants who had undergone uterine artery pulsatility index evaluation at the time of randomization. During each ultrasound examination, the uterine artery pulsatility index was evaluated transabdominally. The mean uterine artery pulsatility index between the progesterone and placebo groups were compared for each gestational age, starting between 18 to 34 weeks and 6days and were analyzed at three (Time 1), six (Time 2) and nine (Time 3) weeks after randomization. RESULTS: The final analysis included 128 women in the progesterone group and 122 women in the placebo group. The baseline characteristics were similar in both groups. No difference in the mean uterine artery pulsatility index was observed between the progesterone and placebo groups at each week of gestation or throughout gestation. CONCLUSIONS: In twin pregnancies, the use of vaginal progesterone in the second half of pregnancy does not influence uterine circulation.