Methotrexate Administration to Patients With Presumed Ectopic Pregnancy Leads to Methotrexate Exposure of Intrauterine Pregnancies.

Objective: To report clinical experience with methotrexate (MTX) treatment for suspected but not definite ectopic pregnancy (EP).

Methods: This was a retrospective cohort study. All patients treated with MTX for presumed EP between 2000 and 2016 were included. Demographic, clinical, sonographic, and outcome data were collected and analyzed.

Results: A total of 820 patients were treated with MTX, 692 (84.4%) of which were lacking definitive features of EP; 155 (22.4%) failed to follow up until complete resolution and were excluded. Retrospective sonographic categorization was applied to 537 patients; of those patients, 393 (73.2%) were categorized as probable EPs, 136 (25.3%) pregnancies of unknown location (PULs), and 8 (1.5%) probable intrauterine pregnancies (IUPs). Sixteen were eventually diagnosed with IUP: 6 from the probable EPs, 9 from the PULs, and 1 from the probable IUP group. Patients with final diagnosis of IUP had higher values of β-human chorionic gonadotropin as well as lower prevalence of adnexal mass (38% versus 74%; P = .003), higher prevalence of intracavitary fluid (44% versus 9%; P = .0004) and thicker endometrium (17.1 ± 11.8 versus 9.7 ± 5.6; P = .04). None of the sonographic parameters were able to distinguish patients with IUP. One patient of the 16 with IUP was diagnosed with a viable pregnancy, and 7 additional patients had a possible viable pregnancy. None of them elected to continue the pregnancy.

Conclusions: Most patients with suspected EP who are eligible for medical treatment lack definitive sonographic features of EP. Treatment with MTX in such cases should be delayed, as clinically reasonable, to improve the diagnosis and prevent inadvertent administration of MTX to patients with a viable IUP.