In ectopic pregnancy (EP) management, failure of βhCG to fall more than 15% between Days 4 and 7 after methotrexate administration indicates the need for a second dose. Regimens preferring a 25% fall in βhCG between methotrexate administration and Day 7 have been proposed.

Our study analysed these and other regimens’ performance in predicting treatment success. Secondarily, we investigated how each regimen guided the prescription of additional methotrexate doses.

Medical files of 88 women with ultrasound confirmed tubal EP and pretreatment βhCG <6000 IU/L, unsuitable for expectant management, were retrospectively analysed. The βhCG monitoring regimens studied were (i) 15% fall Day 4–7, (ii) 25% fall Day 0/1–7, (iii) any fall Day 0/1–7, (iv) any fall Day 0/1–4 and (v) 20% fall Day 0/1–4. Treatment success was defined if the EP resolved without surgical intervention. Statistical analysis was performed using McNemar's test. Results Overall, treatment success with methotrexate was 92% (n = 81/88). Predicting success of methotrexate (PPV 98–100%) and detecting those needing surgery (specificity 86–100%) were equivalent across all monitoring regimens. However, the 25% Day 0/1–7 fall (and the Day 0/1–4 regimens) over‐selected women for a second dose of methotrexate (P < 0.05). Conclusion The performance of each regimen is equivalent to the traditional 15% fall Day 4–7 regimen in predicting treatment success. However, a regimen aiming for a 25% fall in βhCG Day 0/1–7 over‐selects patients for a second methotrexate dose. In comparison, any drop in βhCG Day 0/1–7 does not over‐select women and eliminates Day 4 testing.