Background: The use of methotrexate for the treatment of women with tubal ectopic pregnancies is now common practice. However, the clinical and hormonal determinants of the success of this treatment are not known.
Methods: We studied 350 women with tubal ectopic pregnancies who were treated with methotrexate intramuscularly according to a single-dose protocol. Pretreatment serum concentrations of human chorionic gonadotropin and progesterone, the size and volume of the gestational mass, fetal cardiac activity, and the presence of fluid (presumably blood) in the peritoneal cavity were correlated with the efficacy of therapy, as defined by resolution of the ectopic pregnancy without the need for surgical intervention.
Results: There was no relation between the women's age or parity, the size or volume of the conceptus, or the presence of fluid in the peritoneal cavity and the efficacy of treatment. Among the 320 women in whom treatment was successful (91 percent), the mean (+/-SD) serum chorionic gonadotropin and progesterone concentrations were 4019+/-6362 mIU per milliliter and 6.9+/-6.7 ng per milliliter (21.9+/-21.3 nmol per liter), respectively, as compared with 13,420+/-16,590 mIU per milliliter and 10.2+/-5.5 ng per milliliter (32.4+/-17.5 nmol per liter) (P<0.001 and P=0.02) in the 30 women in whom treatment was not successful. Fetal cardiac activity was present in 12 percent of the successfully treated cases and 30 percent of those in which treatment was not successful (P=0.01). Regression analysis revealed the pretreatment serum chorionic gonadotropin concentration to be the only factor that contributed to the failure rate.
Conclusions: Among women with tubal ectopic pregnancies, a high serum chorionic gonadotropin concentration is the most important factor associated with failure of treatment with a single-dose methotrexate protocol.