To determine the rate of induced abortions in women with rheumatoid arthritis (RA) exposed to methotrexate (MTX) compared with women with RA unexposed to this medication.
We performed a nested case-control study using administrative databases from Quebec. All women with RA ages 15-45 years were identified and cases were defined as women having an induced abortion. Each case was matched to ≥1 controls for age, calendar time, and cohort entry. Exposure was defined as having filled ≥1 prescriptions of MTX ≤16 weeks prior to the index date.
We identified 112 cases of induced abortions in women with RA and 5,855 RA controls. Exposure to MTX occurred in 10.7% of cases and 21.7% of controls. Women exposed to MTX had a lower rate of induced abortions compared with unexposed women (rate ratio [RR] 0.47 [95% confidence interval (95% CI) 0.25-0.89]). In the multivariate analysis, there was a trend toward an increased rate of induced abortions among women exposed to anti-tumor necrosis factor (anti-TNF) agents (RR 2.07 [95% CI 0.81-5.27]).
Women with RA exposed to MTX have a lower rate of induced abortions than unexposed women. Women with RA exposed to anti-TNF agents may have an increased rate of induced abortions compared to unexposed women.