Interstitial pregnancy (IP) is a type of ectopic pregnancy in which the embryo implants in the interstitial part of the Fallopian tube. It accounts for 2% of all ectopic pregnancies. Signs and symptoms appear later than the other forms of ectopic pregnancies because of its peculiar location. The gold standard for its diagnosis is transvaginal ultrasound. The treatment can be medical or surgical. Medical treatment is based on the systemic or local injection of methotrexate (MTX); a dose of mifepristone can be added with a reported 85-90% success rate. The surgical option is laparoscopic unilateral cornuostomy or unilateral salpingectomy. The therapeutic choice is based on symptoms, serum β-human chorionic gonadotropin (β-hCG) values, and sonographic features. Furthermore, the patient's fertility perspectives should be considered. We report a case of IP in a Caucasian woman of 29 years old, with a previous salpingectomy for ectopic pregnancy medically treated by a double dose of intramuscular MTX 50 mg/m2 combined with a single dose of leucovorin 15 mg and a single dose of mifepristone 600 mg orally. Medical therapy failed as suggested by the sudden onset of intense pelvic pain after 10 days. Because of the clinical symptoms and the sonographic suspicious of pregnancy rupture due to the modest amount of fluid in the pouch of Douglas, clinicians decided on an urgent unilateral laparoscopic salpingectomy. The hemoperitoneum was drained. The patient was discharged two days later and β-hCG serum levels became negative after 45 days. The advantages of fertility sparing should be weighted according to the patient's reproductive perspectives. Appropriate counseling is therefore key in managing the treatment of interstitial pregnancy.
