Objective: To investigate the blood flow and progesterone levels in non-pregnant women with a history of unexplained recurrent pregnancy loss (RPL) in comparison to normal fertile women. Patients and methods: This case control study was done at Department of Obstetrics and Gynecology in Beni-Suef University from October 2020 to April 2021. Cases with history of unexplained RPL (n = 55), and controls with no history of miscarriage and at least one term delivery (n = 55). Serum progesterone measurement and transvaginal uterine artery Doppler were conducted to all participants in the midluteal phase to assess the uterine artery pulsatility index (PI), resistance index (RI) and serum progesterone level. Results: Uterine artery PI and RI were significantly higher in the study group (p < 0.001). On the other hand, there was no significant difference in serum progesterone level between the two groups(p=0.855). The cut-off value of uterine artery RI > 0.85 and the cut-off value of uterine artery PI > 2.3 were significantly associated with unexplained RPL. Conclusions: This study concluded that serum progesterone had no role in prediction of unexplained RPL. Uterine artery PI and RI had a role in prediction of unexplained abortion, but the PI is better than RI in the prediction of unexplained RPL.