Gynaecology & Obstetrics Which of the following would be most likely causing methotrexate therapy failure in ectopic pregnancy treatment. A Multiparous woman B Ectopic size > 2.5 cm C Previous history of ectopic pregnancy D Serum β hcG level of 9000 mIU / mL. 💡 Explanation Which of the following would be most likely causing methotrexate therapy failure in ectopic pregnancy treatment. ✓ Correct Answer: D. Serum β hcG level of 9000 mIU / mL.