Oral Corticosteroid Use During Pregnancy and the Risk of Gestational Diabetes

Importance Oral corticosteroids (OCSs) are increasingly used during pregnancy for various conditions due to their immunosuppressive and anti-inflammatory properties. However, OCSs may induce insulin resistance, potentially contributing to gestational diabetes, and limited studies have examined this association. Objective To assess the risk of gestational diabetes associated with OCS use during pregnancy. Design, Setting, and Participants This nationwide, population-based cohort study included pregnancies resulting in live births in Korea from 2010 through 2021. A sequential landmark analysis was conducted, with OCS exposure assessed in 3-week intervals between 1 and 27 weeks’ gestation. Data were analyzed from June 26, 2024, to September 19, 2025. Exposure Pregnancies among women who were exposed to OCSs were compared with pregnancies among women who were not exposed to OCSs within each 3-week interval and in pooled analyses. Main Outcomes and Measures Gestational diabetes was assessed from 20 weeks plus 1 day of gestation until delivery using a previously validated algorithm. Propensity score–based overlap weighting was applied to adjust for comorbidities, medication use, and health care utilization. Risk ratios (RRs) and 95% CIs were estimated using bootstrapping with 200 replications. Subgroup analyses by age, indication, duration of action, dose, timing, and duration of exposures were performed. Results Among 3 848 270 pregnancies, 1 325 940 were eligible for analysis, of which 79 710 (6.0%) were exposed to OCSs between 1 and 27 weeks’ gestation. OCS exposure was not associated with an increased risk of gestational diabetes in most intervals, except between 4 and 6 weeks’ gestation (weighted RR, 1.10; 95% CI, 1.03-1.17). In the pooled analysis, gestational diabetes occurred in 9.50% (95% CI, 9.26%-9.74%) of pregnancies among women in the exposed group vs 7.36% (95% CI, 7.31%-7.43%) of pregnancies among those in the unexposed group (weighted RR, 1.01; 95% CI, 0.99-1.03). Subgroup analyses showed no significant effect modification by maternal age, indication, duration of action, dosage, timing, or duration of exposure. Conclusions and Relevance In this cohort study, OCS exposure during pregnancy was not associated with an increased risk of gestational diabetes, except for a modest increase in risk among women exposed to OCSs between 4 and 6 weeks’ gestation, supporting the use of OCSs when clinically indicated.