Interstitial Pregnancy Treated with Mifepristone and Methotrexate with High Serum β-hCG Level in a Patient Wishing to Preserve Fertility: Time to Define Standardized Criteria for Medical/Surgical Therapy?

Interstitial pregnancy (IP) accounts for 2% of all ectopic pregnancies and has a mortality rate of 2-2.5%. The diagnosis is made by a transvaginal ultrasound and the treatment can be medical or surgical. We report the case of a 36-year-old primigravida who was 6 + 5 weeks pregnant, diagnosed with interstitial pregnancy by ultrasound, who had a very high serum β-hCG level (31,298 mIU/mL) and wanted to preserve her fertility. The patient was treated with one dose of mifepristone and a double dose of methotrexate since the decrease in the β-hCG serum level was less than 15% after the first dose. At the beginning, medical therapy was effective, as no embryonal cardiac activity was detected and serum β-hCG levels decreased early, but on the 20th day of hospitalization, the patient underwent surgery for her clinical symptoms and the evidence of free fluid in the Douglas pouch at a transvaginal ultrasound exam. Our experience showed that medical treatment should be considered, especially in women wishing to preserve their fertility. Further studies are needed to establish a standardized protocol and maybe a clinical score that can be useful in predicting the patients in which medical therapy could be most successful.