In the last three decades, systemic methotrexate (MTX) has become widely accepted as the primary treatment for unruptured tubal pregnancy. This has prompted investigations into the use of MTX in the management of interstitial pregnancy.

To determine the effectiveness of methotrexate for treatment of interstitial pregnancy.

We retrospectively reviewed 17 haemodynamically stable women admitted to our tertiary, university‐affiliated medical centre with an intact interstitial pregnancy from January 2003 through February 2013. First‐line treatment consisted of intramuscular MTX 1 mg/kg/day x4 alternating with folinic acid 0.1 mg/kg or, in cases of low beta‐human chorionic gonadotropin (β‐hCG) and no embryonic pole, one dose of 50 mg/m2 body surface area. Uterine artery MTX injection was administered on the ipsilateral side of the pregnancy followed by uterine artery embolisation as second‐line treatment. Failure criteria were <15% decrease in β‐hCG or sonographic evidence of pregnancy development. Second‐line failures were referred for surgery. Results Twelve women (70.5%) underwent successful first‐line treatment and 5 (29.5%) required second‐line treatment. Baseline characteristics were similar except for a higher rate of two previous ectopic pregnancies in the first‐line failures (80% versus 8.3%, P = 0.01). Two women eventually required surgery, both with two previous ectopic pregnancies. Of the three women with fetal cardiac activity on admission, two had successful first‐line treatment and one required surgery. Conclusion Systemic MTX is effective for treatment of intact interstitial pregnancy in haemodynamically stable women. The success rate is increased with uterine artery MTX injection as second‐line treatment.