Objective: To determine whether the amount of intrauterine tissue was prognostic of the risk of complications associated with the management of nonviable pregnancies diagnosed in the first trimester before cervical dilatation (termed here impending abortion) with either expectant observation or elective curettage. Design: Historic cohort study. Setting: University Infertility Service. Patient(s): All women with nonviable pregnancies followed by the Division of Reproductive Endocrinology during a 5-year period. The patients were divided into those with significant intrauterine tissue (gestational sac > 10 mm) and those with minimal intrauterine tissue. Intervention(s): Women either underwent elective curettage or were followed expectantly. Main Outcome Measure(s): Complication rates. Result(s): In 89 women with minimal tissue, no complications occurred regardless of treatment mode. In 63 women with significant intrauterine tissue, expectant management resulted in more complications (9/24) than elective curettage (1/39). In the expectant group, complications included missed abortion, septic abortion, and incomplete abortion requiring emergency curettage, with one patient requiring a transfusion. In the curettage group one uterine perforation occurred. Conclusion(s): In women with impending abortions and minimal intrauterine tissue, expectant treatment is safe after ectopic pregnancy has been excluded. In patients with significant intrauterine tissue, the risk of complications may be decreased by elective uterine curettage compared with expectant management.