ObjectiveTo determine whether the incidence of gestational diabetes mellitus (GDM) is increased in patients receiving corticosteroids with or without β-adrenergic agents for threatened preterm delivery.MethodsWe reviewed the laboratory records of 3396 patients undergoing screening (1-hour glucose) and diagnostic testing (3-hour glucose tolerance test [GTTD FOR GDM over 2 years. Patients with antepartum admissions during jwhich they received corticosteroids with or without β-adrenergic agents for threatened preterm delivery were compared with a control group during group during e same period. Differences between the study and control groups were analyzed using χ2, Studentttest, or Fisher exact test where appropriate.P< .05 was considered significant.ResultsFifty patients in the study group were compared with 1985 control patients. The ramaining 1361 patients failed to meet inclusion criteria. The overall incidence of diagnosed GDM was significantly greater in the corticosteroid-β-adrenergic agents study group, in which five (23.8%) of 21 patients screened had abnormal 3-hour GTT results, compared with 79 (4.%) of 1985 controls (P= .001). One- Hour glucose screening test results were abnormal in 60% of the study group compared with 25% of the controls (P< .001).ConclusionPatients treated with β-adrenergic agents and corticosteroids for threatened preterm delivery are at a significantly increased risk for developing GDM. The high rate of abnormal results in response to the 1-hour glucose screen suggests that this test is of limited value in patents exposed to these medications.