Aims: The relationship between oxidative stress and the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria diagnosed gestational diabetes mellitus GDM isn't well known. Our aim is to evaluate the oxidative stress in women diagnosed by the IADPSG criteria versus the American Diabetes Association (ADA) criteria in China. Methods: Malondialdehyde (MDA), 8-isoprostane (8IsoP), xanthine oxidize (XO), lipid peroxides (LPO), superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (TAC), vitamin C (Vc) and vitamins E (Ve) were determined in maternal and cord plasma and placenta of 68 pregnant women. Among these, 28 were diagnosed with GDM while the other 40 were controls. Results: The maternal, cord and placental MDA, XO and 8IsoP levels were significantly higher while SOD and TAC levels were significantly lower in GDM women by either criterion (P < 0.05). XO and 8IsoP levels were higher in ADA group than IADPSG only group while TAC levels significant lower (P < 0.05). Cord MDA, cord and placental XO, and maternal and cord 8IsoP showed significant positive relationship with HbA1c values (P < 0.05). Cord XO levels increased (P < 0.05) while maternal and placental SOD levels decreased (P < 0.05) in women who received cesarean section compared with those delivered normally. Increased XO levels and decreased Ve levels in cord plasma were also found in macrosomia (P < 0.05). Conclusions: Oxidative stress is present in women diagnosed by IADPSG but to a lesser degree than by ADA. All these women should be monitored and perhaps antioxidant supplemented. (C) 2015 Elsevier Ireland Ltd. All rights reserved.