ABSTRACT: OBJECTIVE:Some atypical antipsychotics are associated with metabolic side effects, which are risk factors for gestational diabetes. The authors examined the risk of developing gestational diabetes associated with the continuation of treatment with aripiprazole, ziprasidone, quetiapine, risperidone, and olanzapine during pregnancy compared with discontinuation of these antipsychotic drugs. METHOD:Nondiabetic pregnant women who were linked to a live-born infant and enrolled in Medicaid (2000-2010) and who received one or more prescriptions dispensed for an antipsychotic drug during the 3 months before pregnancy were included in the analyses. Among 1,543,334 pregnancies, some expectant mothers at baseline were receiving treatment with aripiprazole (N=1,924), ziprasidone (N=673), quetiapine (N=4,533), risperidone (N=1,824), or olanzapine (N=1,425). For each antipsychotic drug, women with two or more dispensings ("continuers") were compared with women with no dispensings ("discontinuers") during the first half of pregnancy. A generalized linear model and propensity-score stratification were used to obtain absolute and relative risks of developing gestational diabetes, with adjustment for confounders. RESULTS:Women who continued antipsychotic treatment during pregnancy generally had higher comorbidity and longer baseline antipsychotic use. The crude risk of developing gestational diabetes among continuers compared with discontinuers, respectively, was 4.8% and 4.5% for aripiprazole, 4.2% and 3.8% for ziprasidone, 7.1% and 4.1% for quetiapine, 6.4% and 4.1% for risperidone, and 12.0% and 4.7% for olanzapine. The adjusted relative risks were 0.82 (95% CI=0.50-1.33) for aripiprazole, 0.76 (95% CI=0.29-2.00) for ziprasidone, 1.28 (95% CI=1.01-1.62) for quetiapine, 1.09 (95% CI=0.70-1.70) for risperidone, and 1.61 (95% CI=1.13-2.29) for olanzapine. CONCLUSIONS:Compared with women who discontinued use of an atypical antipsychotic medication before the start of pregnancy, women who continued treatment with olanzapine or quetiapine had an increased risk of gestational diabetes that may be explained by the metabolic effects associated with these two drugs.