It is known that atosiban has fewer side effects than conventional tocolytics. In clinical practice, however, hyperglycemia can be commonly observed in mothers who have been administered atosiban. Therefore, we investigated whether intravenous atosiban injection actually causes hyperglycemia and how these changes affect newborns. From December 2015 to July 2018, a retrospective study was conducted on 96 mothers who were diagnosed with preterm labor and were administered atosiban at our institution. Maternal blood glucose was measured and compared before and during the administration of atosiban. The paired t-test, independent samples t-test, Chi-square test and Fisher’s exact test were performed using SPSS version 21.0. A statistically significant increase in fasting blood glucose levels was observed during the administration of atosiban, compared with random blood glucose levels before administration (110.7 mg/dL vs. 86.3 mg/dL). The mean postprandial blood glucose level during administration was 170.75 mg/dL. Gestational diabetes, twin pregnancy, preeclampsia, and polyhydramnios did not significantly affect the degree of blood glucose increase. Statistically significant hypoglycemia was observed after performing a neonatal blood test immediately after birth from mothers who used atosiban. The neonates from the group with elevated maternal blood glucose levels exceeding 20 mg/dL showed lower blood glucose levels. No serious side effects other than hypoglycemia were observed. Atosiban administration in pregnant women results in significantly elevated maternal blood glucose, which results in hypoglycemia in neonates after birth. Therefore, neonates from mothers who received atosiban require a blood glucose test and close monitoring after birth.