Background/Purpose: Disease-modifying antirheumatic drugs (DMARDs) are the primary class of drug therapies generally used to treat rheumatic diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriatic arthritis (PsA), and ankylosing spondylitis (AS). However, the safety effects of DMARD use during pregnancy remain largely understudied, despite many individuals continuing some form of DMARD therapy during pregnancy to control maternal disease activity. Within Canada, past observational studies have leveraged claims data from the provinces of Quebec and British Columbia to study DMARD safety in pregnancy. This study aimed to assess the risk of severe maternal morbidity (SMM) and severe neonatal morbidity (SNM) in individuals with rheumatic diseases using DMARDs during pregnancy in Ontario, Canada’s most populous province.

Methods: Leveraging routinely collected population-based healthcare administrative claims data at ICES in Ontario, Canada, we included pregnant individuals with RA, SLE, PsA, and/or AS who delivered a liveborn or stillborn singleton infant after 20 weeks of gestation between April 1, 2006, and March 31, 2021. DMARD exposure was defined as having at least one conventional synthetic or biological DMARD dispensation reimbursed from estimated conception to delivery. To adjust for confounders such as maternal age, rheumatic conditions and comorbidities, healthcare utilization, and concomitant medication use, propensity scores were calculated to estimate the probability of DMARD exposure. Stabilized inverse probability of treatment weights were derived from propensity scores and used in logistic regression modelling to estimate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for SMM and SNM in the DMARD-exposed cohort versus unexposed comparators.

Results: There were 836 pregnant individuals with rheumatic conditions, with 302 exposed to DMARDs and 534 unexposed. Most individuals had a diagnosis of RA (n=396, 47.4%), followed by SLE (n=357, 42.7%), AS (n=86, 10.3%), and PsA (n=48, 5.7%), with 49 (5.9%) individuals having more than one of these conditions. In unadjusted analyses, DMARD exposure was associated with SMM (OR: 1.81, 95% CI: 1.11–2.96) but not associated with SNM (OR: 0.97, 95% CI: 0.62–1.51). After adjusting for confounders, DMARD exposure was not associated with SMM (OR: 1.47, 95% CI: 0.86-2.51) or SNM (OR: 0.94, 95% CI: 0.59-1.49). Sensitivity analyses using overlap weights, entropy weights, and a longer exposure window from six months before estimated conception to delivery did not yield significant changes in point estimates and confidence intervals.

Conclusion: These findings suggest that DMARD use before and during pregnancy is not associated with an increased risk of SMM or SNM. Further studies with larger sample sizes are needed to better understand the long-term maternal and neonatal outcomes associated with prenatal DMARD use and develop real-world evidence-based clinical guidelines for safe prescribing during pregnancy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-of-adverse-pregnancy-outcomes-in-individuals-with-rheumatic-diseases-using-prenatal-antirheumatic-drugs-a-population-based-cohort-study/