Conservative treatment for interstitial monochorionic twin pregnancy: case report and review of the published work.

Interstitial pregnancy is considered one of the most hazardous types of ectopic pregnancies, with a mortality rate of 2-2.5%. We describe a case of a viable monochorionic twin pregnancy in a 35-year-old woman successfully treated with systemic methotrexate associated with bilateral uterine arteries' embolization. β-hCG was undetectable 67 days after the first administration of methotrexate and the ultrasonography performed on day 67 showed the remnant of the gestational sac in the right uterine horn, a thin endometrium and a normal myometrial vascularization. Conservative treatment allowed us to avoid surgical treatment and to preserve the patient's fertility.