Background: Previous research declares that gestational diabetes mellitus (GDM) affects both mother and infant during pregnancy and in the long term. Objective: To assess the pattern of DNA damage in mothers with gestational diabetes during pregnancy and their possible impact on their offspring. Patients and Methods: A case-control study was designed and conducted on 120 pregnant women and their infants; divided into two groups: 1-Patients group (60 patients had gestational diabetes mellitus during the third trimester of pregnancy and their infants) 2-Control group (60 apparently healthy pregnant women and their infants). Results: DNA damage of mother and their infants was significantly increased among the cases group than controls (p=0.0001). There was a statistically significant increase among infants who had DNA damage group than who hadn't regarding HBA1C, random blood sugar (RBS) 3 hr and RBS 6 hr (p < 0.05). Also, infants who had DNA damage had statistically significant decrease regarding Ca, RBS 24 hr, RBS 36 hr and RBS 48 hr (p < 0.05). While there was no statistically significant difference between the studied groups regarding Hb, hematocrit, RBS, fasting BS, AST, Hemoglobin (Hb) at 1 hr, hematocrit at 1 hr, Hb 24 hr, hematocrit 24 hr, RBS 1hr, RBS 2 hr and RBS 12 hr (p>0.05). Conclusions: Hyperglycemia affects maternal and fetal DNA integrity and DNA damage response differently, gestational and mild gestational hyperglycemia, were all related to increased oxidative DNA damage and DNA repair may be thus considered an important mechanism to prevent the deleterious effects of hyperglycemia in the genetic material.