Aim. Antenatal glucocorticoid therapy (AGT) has been commonly used recently. However, this therapy has severe harmful effects such as maternal hyperglycemia. In Japan, ritodrine hydrochloride has been used as a tocolytic agent. In this study, we performed retrospective casecontrol study to clarify whether concomitant use of ritodrine and glucocorticoid was safe to pregnant women without diabetes mellitus. Methods. We reviewed the computerized records of pregnant women with pregestational diabetes (n = 9) and nondiabetes (n = 45) who gave birth at our hospital between 2002 and 2011. Cases and controls received AGT. Blood glucose after the therapy was analyzed, and additional volume of insulin was compared to that before the therapy. Results. From this study, 30 units of insulin were necessary when performing AGT in diabetic pregnant women. And also, an increase in blood glucose of 40 mg/dL was seen after the therapy even in nondiabetic pregnant women. Blood glucose increased significantly in the group that also received ritodrine, and it was shown that the number of pregnant women who might develop ketoacidosis might increase 11-fold. Conclusions. Ritodrine should be carefully administered during antenatal glucocorticoid therapy. It may be necessary to adequately monitor blood glucose, when performing the therapy, even in nondiabetic pregnant women.