Background/Purpose: Infection risk is one of the concerns regarding therapy with conventional disease modifying antirheumatic drugs (csDMARDs) and to our knowledge no research has examined this concern in pregnancy.  Our objective was to evaluate the association between exposure to csDMARD during pregnancy and risk of serious infections in women with inflammatory arthritis (IA).

Methods: Linking population-based administrative data on all physician visits, hospital admissions, and all dispensed medications to a provincial perinatal registry, we conducted a retrospective cohort study from 01/01/2002 and 12/31/2012.  Unique to this registry is detailed information on antenatal, intrapartum, and postpartum maternal and infant outcomes as well as valid information on date of conception. We created a pregnancy cohort of women with IA using a case definition of 2 outpatient physician ICD9 codes within 2 months and less than 2 years apart for rheumatoid arthritis, systemic autoimmune rheumatic diseases, and other IA. We categorized csDMARDs according to accepted compatibility with pregnancy: Group 1 – antimalarials, cyclosporine, gold, sulfasalazine; and Group 2 – azathioprine, chlorambucil, cyclophosphamide, leflunomide, methotrexate, minocycline, mycophenolate mofetil, pencillamine. We ascertained exposure during pregnancy as binary use (yes/no) overall and according to the most recent trimester. Serious maternal infection outcomes were those requiring hospitalization during the first 42 days post-partum. We used Poisson regression models to evaluate the association between csDMARD during pregnancy and serious maternal infections, adjusting for baseline covariates.

Results: There were 485 pregnancies in 405 women, and 5,764 pregnancies in 4,168 women in the csDMARDs exposed and unexposed groups, respectively, during the study period (Table 1). We identified 3.5%, 3.9%, and 4.0% of mothers with serious infections in unexposed pregnancies and those exposed to Group 1 and 2 csDMARDs, respectively. As shown in Table 2, there were no associations with csDMARDs use during pregnancy and serious infections in mothers when considering overall exposure (adjusted odds ratio [OR], 0.96; 95% confidence interval [CI], 0.60 to 1.54) or according to trimester. Findings persisted in sub-analyses according to csDMARD groups.

Conclusion: We found no association with exposure to csDMARDs during pregnancy and serious maternal infections among women with IA.  These findings have implications for informing women with IA who are pregnant or planning to become pregnant.