Low-dose methotrexate treatment for interstitial pregnancy. A case report

Only a small number of case reports have described medical treatment of interstitial ectopic pregnancies. Almost all of the reported patients were treated with repeated high doses (1 mg/kg) of methotrexate.

At 6 weeks of gestation, a 31-year-old woman, gravida 5, para 4, was diagnosed with a 0.96 x 1.36-cm right cornual pregnancy. As the patient desired future fertility, she received 100 mg of intramuscular methotrexate (50 mg/m2). She was then followed on an outpatient basis, with serum human chorionic gonadotropin values appropriately declining. Serial ultrasound also showed decreasing size of the gestational sac. Twenty-one days after the methotrexate dose, the patient experienced rupture of the right posterior cornu, necessitating exploratory laparotomy.

Extreme caution should be used when treating interstitial gestations with single-dose methotrexate. All patients should be extensively counseled regarding the significantly increased risk of failure, possibility of rupture and need for emergency surgery.