['To assess the incidence of retained products of conception (RPOC) in relation to transvaginal ultrasound performed after first-trimester uterine evacuation.', 'This was a prospective randomized study involving 809 women undergoing first-trimester uterine evacuation. The study group included 404 women in whom transvaginal sonography was performed at the end of the surgical procedure and the control group contained 405 women who did not undergo ultrasound examination. Initially, in the study group, recurettage was immediately performed if the endometrium appeared irregular but latterly only if endometrial thickness was > or = 8 mm. The patients were followed up by gynecological and ultrasound examinations 5-8 days following the surgical procedure.', 'The total complication rate was 4.3%. RPOC presented in three women in the study group (0.7%) and in 15 women in the control group (3.7%, P < 0.05). Vaginal bleeding requiring hospitalization occurred in two women in the study group (0.5%) vs. seven in the control group (1.7%, P = 0.2). Endometritis was diagnosed in one woman in the study group (0.2%) vs. six in the control group (1.5%) and uterine perforation occurred in one woman in the control group vs. none in the study group. There were no cases of RPOC in women who had an endometrial thickness of < 8 mm as demonstrated by ultrasound at the end of the surgical procedure.'] Does transvaginal ultrasound after first-trimester uterine evacuation reduce the incidence of retained products of conception?