Oral corticosteroid use during pregnancy and risk of preterm birth

Objective: To evaluate the associations between oral corticosteroid (OCS) dose early and late in pregnancy and preterm birth (PTB) among women with RA.

Methods: Pregnant women in the MotherToBaby Pregnancy Studies (2003-2014) with RA (n = 528) were included in the primary analysis. Information was collected by phone interview and from medical records. We estimated risk ratios (RR) for OCS dose trajectories and other disease-related medications before gestational day 140 and hazard ratios (HR) for time-varying exposures after gestational day 139.

Results: PTB risk was 15.5% overall. Compared with no OCS, PTB risk was increased in high (adjusted (a)RR: 4.77 (95% CI: 2.76, 8.26)) and medium (aRR: 1.81 (95% CI: 1.10, 2.97)) cumulative OCS dose trajectories during the first 139 gestational days. The low cumulative trajectory group was associated with an increased risk of PTB that was not statistically significant (aRR: 1.38 (95% CI: 0.79, 2.38)), and DMARDs were not associated with PTB (biologic DMARDs aHR: 1.08 (95% CI: 0.70, 1.66); non-biologic DMARDs aHR: 0.87 (95% CI: 0.55, 1.38)). OCS exposure to ⩾10 mg of prednisone equivalent daily dose after gestational day 139 vs none was associated with increased PTB rate (aHR: 2.45 (95% CI: 1.32, 4.56)), whereas <10 mg was associated with a modestly increased rate of PTB that was not statistically significant (aHR: 1.18 (95% CI: 0.60, 2.30)).

Conclusion: Higher OCS doses vs no OCS use, both earlier and later in pregnancy, were associated with an increase in PTB among women with RA.