Uterine artery Doppler is frequently used in the first trimester and it is one of the more effective measurement methods in the prediction of preeclampsia and intrauterine growth restriction (IUGR). Progesterone is a hormone that is used quite frequently in various indications in obstetrics and gynecologic practice. We aimed to investigate the influence of progesterone on the uterine artery Doppler pulsatility index (PI) at 11-14 gestational weeks.This study is a retrospective case-control study conducted in Selcuk University Faculty of Medicine between January and December 2019. Uterine artery Doppler PI values of patients using progesterone were compared with PI values of patients not using progesterone. Uterine artery PI was measured two times, left and right. Then the mean PI was calculated. All measurements were made by two operators and by the same ultrasonography machine RESULTS: A total of 288 patients, 140 patients using progesterone and 148 patients not using progesterone were included in the study. Demographic characteristics were similar between the groups (p > 0.05). There were no significant differences between the groups in the right and left uterine artery PI values. There was no significant difference for average uterine artery PI between the groups (p < 0.05).Progesterone has no significant influence on uterine artery PI. However, more prospective studies in which all potential confounding factors are considered including serum progesterone levels are needed for this subject.