The purpose of this study was to evaluate the diagnostic accuracy of transvaginal sonography for first trimester spontaneous abortions, thought to be incomplete or complete, in patients with postabortion bleeding or uterine cramping within 5 days of abortion. In a prospective study, 78 patients underwent transvaginal sonography to evaluate the maximum anteroposterior diameter of the uterine cavity on the long axis view and echo pattern of the retained products of conception. Patients were divided into three groups: those with a normal uterine cavity or a uterine cavity with fluid collection without echogenic foci (n = 13, group A), those with a uterine cavity containing fluid mixed with solid components (n = 38, group B), and those with a uterine cavity containing solid components (n = 27, group C). Group A was considered not to have retained products of conception, and the latter two groups were considered to have retained products of conception. Patients in group A were assigned to receive conservative treatment. In groups B and C, patients with significant vaginal bleeding during 48 h of follow-up underwent effective curettage and those with minimal-mild bleeding received conservative management. A total of 73 patients (12 in group A, 35 in group B, and 26 in group C) completed the study. There were no differences in any of selected reproductive data of the groups (p >0. 05). In group B, all patients with uterine cavity diameter of 10 mm or greater underwent elective curettage. In group C, all patients with a diameter of the uterine cavity 8 mm or greater underwent elective curettage. The overall complication and patient satisfaction rates were approximately 14% and 88%, respectively. Transvaginal sonographic findings can be used as a decision factor in the management of patients with first trimester spontaneous abortion to reduce the need for an elective curettage by approximately 58%. CONTRACEPTION 1998;57:393-397 (C) 1998 Elsevier Science Inc. All rights reserved.