ObjectiveTo investigate whether the incidence of persistent ectopic pregnancy after linear salpingostomy can be reduced by prophylactic administration of a single dose of methotrexate postoperatively.MethodsWomen who underwent linear salpingostomy for treatment of unruptured ectopic pregnancy and who agreed to participate in the study (n= 129) were randomly assigned to the prophylaxis or control group. Women with anemia, renal insufficiency, or liver disease were excluded. In the prophylaxis group, patients received a single dose of methotrexate, 1 mg/kg intramuscularly, within 24 hours postoperatively. No treatment was used in the control group. Both groups were followed with serial serum β-hCG titers; titers were measured on the seventh postoperative day, then every 72 hours until levels were lower than 15 mIU/mL. A blood count and chemistry panel were also obtained on postoperative day 7, and any side effects related to methotrexate were noted. Persistent ectopic pregnancy was defined as a rise in the serum β-hCG level or a decline of less than 20% between two consecutive measurements taken 3 days apart.ResultsA total of 116 women completed the postoperative follow-up: 54 in the prophylaxis group and 62 in the control group. Ten women had persistent ectopic pregnancy, one in the prophylaxis group (1.9%) and nine among the controls (14.5%); this difference was statistically significant (P< .05). The relative risk of developing persistent ectopic pregnancy after prophylactic methotrexate was 0.13 (95% confidence interval 0.02, 0.97). Three women (5.5%) reported mild side effects after methotrexate, but these resolved spontaneously.ConclusionThe incidence of persistent ectopic pregnancy was significantly reduced after a single prophylactic dose of systemic methotrexate administered postoperatively. This regimen is safe and can be used to decrease the extent of postoperative monitoring after conservative treatment of unruptured ectopic pregnancy.