OBJECTIVE: To estimate whether follow-up with serum human chorionic gonadotropin (hCG) results in fewer unplanned visits and interventions than follow-up with ultrasonography. METHODS: Women were randomized to either in-clinic serum hCG or ultrasound follow-up after medical abortion. The primary outcome, unplanned interventions and visits, was measured as a composite binary outcome including: additional clinic or emergency room visits, repeat dosing of misoprostol, and surgical evacuation of the uterus. Surveys were administered at initial follow-up and again 1 month after abortion to inquire about unscheduled visits, interventions, and patient satisfaction. Medical records were reviewed for evidence of additional interventions and visits. RESULTS: A total of 376 patients was randomized. Most participants were white (56%), single (83%), nulliparous (63%), and had completed high school (96%). Average participant age was 26±6 years and average gestational age was 46±6 days. Within 2 weeks of abortion, there was no significant difference in the rate of unplanned interventions and visits between arms, 8.2% (13/159) in the serum hCG arm compared with 6.6% (10/151) in the ultrasound arm (relative risk 1.23, 95% confidence interval [CI] 0.56-2.73, P=.60). By 4 weeks postabortion, 4.4% (6/135) in the ultrasound arm and 1.4% (2/142) in the hCG arm had undergone surgical evacuation (relative risk 0.32, 95% CI 0.07-1.54, P=.16). The majority in both the serum hCG (88%) and ultrasound (95%) arms was satisfied with their assigned follow-up method. CONCLUSION: Medical abortion follow-up with serum hCG does not reduce the rate of unplanned interventions and visits compared with ultrasonography. Overall, the number of unplanned interventions is low and both methods of follow-up are acceptable to women.