Body Surface Area versus Weight-Based Methotrexate Dosing in Tubal Ectopic Pregnancy: A Retrospective Cohort Study

Abstract Purpose To compare the clinical efficacy and safety of weight-based versus body surface area–based single-dose methotrexate (MTX) protocols in the medical management of tubal ectopic pregnancy. Methods In this retrospective cohort study, 84 hemodynamically stable patients with tubal ectopic pregnancy treated with systemic MTX between 2020 and 2024 were analyzed. Patients received MTX either at 1 mg/kg or 50 mg/m 2 intramuscularly. Demographic, biochemical and clinical characteristics, early beta-human chorionic gonadotropin (β-hCG) kinetics, need for repeat MTX dosing and surgical intervention, and adverse events were compared between the two dosing strategies. Results Of 84 patients, 56 were treated with the body surface area–based protocol and 28 with the weight-based protocol. Baseline characteristics and initial β-hCG levels were comparable. The need for an additional MTX dose was significantly lower in the body surface area group than in the weight-based group (12.5% vs 32.1%; p = 0.031). Surgical intervention was required in 13 patients (15.4%) without a significant difference between groups ( p = 0.135). No MTX-related adverse events were observed. Conclusion Body surface area–based MTX dosing was associated with a significantly lower need for repeat dosing without increasing the rate of surgical conversion or adverse events. Prospective, adequately powered studies are warranted to optimize MTX dosing strategies in tubal ectopic pregnancy and confirm long-term efficacy and safety.