This study's aim is to investigate whether the rise in β-hCG levels between days 0 and 4 in patients with tubal ectopic pregnancy who have received a single dose of methotrexate has prognostic value in treatment success, and to investigate whether administering a second dose on day 4 enhances treatment success.

Patients diagnosed with ectopic pregnancy and experiencing an increase in β- hCG levels on day 4 after initiation of methotrexate treatment were included in our study. Patients treated with a single dose Methotrexate (MTX) protocol until December 2019 were retrospectively screened from January 2018 to December 2019. Patients receiving a second dose on day 4 until September 2021 were prospectively enrolled from January 2020 to September 2021. A decrease of over 15 % in the β-hCG value after the 4th dose was considered as treatment success.

Treatment success rates were compared between these two groups. 115 patients with ectopic pregnancy were included in the study. A single dose methotrexate protocol was applied in 67 of the patients (Group 1), while an additional dose methotrexate was applied in 48 (Group 2). The treatment was successful in 40 patients (59.7 %) in Group 1 and in 39 patients (81.3 %) in Group 2. The success rate of the treatment was significantly higher in patients who received an additional dose methotrexate protocol (p = 0.014).

This study shows that; it is possible to increase success rates by applying an additional MTX dose on the 4th day in cases with an increase in β-hCG on the 4th day.