Background: Transvaginal Doppler ultrasound is a non-invasive and commonly available screening approach for disorders of placental function early in pregnancy that can be used to predict a range of obstetric issues that can be associated to improper placentation and implantation. The present study aimed to assess uterine artery blood flow in threatened miscarriage using Doppler indices of uterine arteries to predict the fate of threatened miscarriage in 1st trimester. Patients and methods: A comparative study was conducted in Departments of Obstetrics and Gynecology in Zagazig University Hospitals and Kafr Saqr Central Hospital during the period from December 2019 to September 2021. The study included 64 pregnant women divided two groups; Group A (study group), included 32 pregnant women with threatened miscarriage, and Group B (control group) included 32 pregnant women with normal pregnancy. Transvaginal ultrasound Doppler studies of both uterine arteries flow indices including pulsatility index (PI), resistance index (RI) and peak systolic velocity (PSV) were carried out. Result: Peak systolic velocity (PSV) of uterine arteries was significantly higher in group (A) (44.46±16.56) compared to group (B) (26.96±5.97). On the other hand other flow indices did not significantly differ between by Mean the groups. Conclusion: Information regarding the uteroplacental circulation obtained with the use of color Doppler ultrasound could provide relevant and important prognostic information in cases of threatened miscarriage.