The purpose of this study was to determine the success rates of methotrexate in progressing ectopic pregnancies and to correlate them with beta–human chorionic gonadotropin (β-hCG) levels.

This retrospective cohort study that was carried out in a tertiary university-affiliated medical center included women who had been diagnosed with ectopic pregnancies between January 2001 and June 2013. Daily β-hCG follow-up examinations were performed to determine the progression of the ectopic pregnancy. Women with hemodynamically stable progressing ectopic pregnancies received methotrexate (50 mg/m² of body surface). We measured the success and failure rates for methotrexate treatment in correlation to β-hCG level.

One thousand eighty-three women were candidates for “watchful waiting” (β-hCG follow up). Spontaneous resolution and decline of β-hCG levels occurred in 674 patients (39.5%); 409 women (24.0%) had stable or increasing β-hCG levels and were treated with methotrexate. In 356 women (87.0%), the treatment was successful; 53 women (13.0%) required laparoscopic salpingectomy. Compared with prompt administration of methotrexate, our protocol resulted in lower overall success rates for all levels of β-hCG in women with progressing ectopic pregnancies: 75% in women with β-hCG levels of 2500-3500 mIU/mL, and 65% in women with β-hCG levels >4500 mIU/mL. A mathematic model was found describing the failure rates for methotrexate in correlation with β-hCG levels.

The success rates for methotrexate treatment in progressing ectopic pregnancies after daily follow-up evaluation of β-hCG levels are lower than previously reported. This reflects redundant administration of methotrexate in cases in which the ectopic pregnancy eventually will resolve spontaneously.