The purpose of this study was to compare clinical outcomes of conservative management versus surgical evacuation of retained products of gestation after misoprostol treatment for first trimester spontaneous miscarriage using less restrictive transvaginal ultrasound criteria for diagnosing “ empty uterus,” which were managed conservatively. This was a prospective, randomized, controlled trial. Forty six patients who had sonographic features previously regarded as significant retained products of gestation after misoprostol treatment, ie, homogenous intrauterine dimension of more than 11 cm2 in combined transverse and sagittal plane, or those with heterogenous intrauterine contents were consented to randomization. The short term complication rates of those managed conservatively were significantly higher than surgical evacuation ( 37.5% vs 0% , P <. 05). Our previously reported transvaginal ultrasound criteria of homogenous intrauterine dimension of less than 11 cm2 in combined transverse and sagittal planes for defining “ empty uterus,” which requires no further treatment, cannot be “ relaxed” without incurring additional complications. The purpose of this study was to compare the clinical outcomes of conservative management versus surgical evacuation of retained products of gestation after misoprostol treatment for first trimester spontaneous miscarriage using less restrictive transvaginal ultrasound criteria for diagnosed “empty uterus,” which were managed conservatively. This was a prospective, randomized, controlled trial. Forty six patients who had sonographic features first viewed as significantly retained products of gestation after misoprostol treatment, ie, homogenous intrauterine dimension of more than 11 cm2 in combined transverse and sagittal plane, or those with heterogenous intrauterine contents were contended to randomization. The short term complication rates of those managed conservatively were significantly higher than surgical evacuation (37.5% vs 0%, P <.05). Our previously reported transvaginal ultrasound criteria of homogenous intrauterine dimension of less than 11 cm2 in combine d transverse and sagittal planes for defining “empty uterus,” which requires no further treatment, can not be “relaxed” without incurring additional complications.