Background: Vaginal bleeding during the first half of pregnancy occurs in approximately25% of women and about half of these pregnancies terminate in abortion. In many instances a retrochorial hematoma (RCH) is sonographically found. Objective: The aim of the present study was to determine the frequency of a RCH in the group of threatened miscarriages and to examine the possible relationship of parity, previous miscarriages, hematoma size and localization, and duration of vaginal bleeding to pregnancy outcome. Materials and Methods: The study group consisted of 45 women of 852 (5.2 %) referred for ultrasound examination due to vaginal bleeding in the first trimester of pregnancy, who were found to have a RCH in the presence of a singleton live embryo. The control group consisted of 807 women with the same gestational age, with vaginal bleeding, and vital singleton pregnancy without sonographically proven RCH. All were followed with repeated sonograms at seven days intervals until bleeding ceased, the RCH disappeared or abortion occurred. The authors have examined the possible relationship of duration of vaginal bleeding, hematoma size and localization, parity, and previous miscarriages to pregnancy outcome (spontaneous abortion, term or preterm delivery). Results: The researches have shown that the previous miscarriages and deliveries do not affect the occurrence of RCH. In the group with a RCH on the back wall of uterus, as well as repeated bleedings affect higher frequency of spontaneous miscarriages. Hematoma size itself does not affect higher frequency of spontaneous miscarriage. Conclusion: Ultrasound is the method of choice for diagnosing the existence of aRCH. The frequency of RCH in the group of threatened spontaneous miscarriages is 5.2 %. A RCH on the back wall and repeated bleedings affect higher frequency of spontaneous miscarriages.Therapy procedure is based on strict bed rest and administration of: pregnyl, gestagenic drugs, progesterone, antihistamines, and sedatives.