Endometrial thickness as a predictor of methotrexate treatment success in ectopic pregnancy: A prospective cohort study

Aim Ectopic pregnancy (EP) remains a significant cause of first‐trimester maternal morbidity and mortality. Methotrexate (MTX) is an effective non‐surgical treatment for selected early pregnancy cases; however, predicting treatment success remains challenging. Endometrial thickness (ET) has been suggested as a potential predictor, though its clinical utility remains uncertain. Methods In this prospective cohort study, 86 women with diagnosed tubal EP and stable hemodynamic status received a single intramuscular dose of MTX (50 mg/m 2 ). Endometrial thickness was measured via transvaginal sonography. Treatment success was defined as a >15% decline in serum β‐hCG between days 4 and 7 post‐MTX without the need for a second dose or surgery. Logistic regression and ROC analysis were conducted to evaluate predictors of treatment success. Results Treatment was successful in 57% of patients. Responders had significantly thinner endometria (mean ET: 8.09 ± 3.53 mm) compared to non‐responders (11.54 ± 4.07 mm, p < 0.001). An ET cut‐off of 9.5 mm predicted treatment success with 73% sensitivity and 69.6% specificity (AUC = 0.740, p < 0.001). Mass size was also a significant independent predictor, while initial β‐hCG and yolk sac presence were not. Conclusion Endometrial thickness is a significant predictor of MTX treatment success in unruptured EP. An ET ≤9.5 mm is associated with a higher likelihood of response. ET measurement may aid clinicians in selecting patients and developing effective management strategies.