OBJECTIVE: Abnormal glucose metabolism during pregnancy can result in significant adverse outcomes for newborns. This study was designed to investigate the effect of different degrees of impaired glucose tolerance on newborns. METHODS: Glucose challenge test (GCT) and oral glucose tolerance test (OGTT) were performed in pregnant women at 24-28 weeks of gestation. Based on the results of the two tests, their newborn infants were classified into five groups: gestational diabetes mellitus (GDM, n=182), gestational impaired oral glucose tolerance ［GIGT, subdividing into GIGT 1 h (n=57) and GIGT 2-3 h groups (n=156)based on the occurrence time of abnormal blood glucose after glucose load］, GCT abnormal but OGTT normal (only GCT abnormal, n=38) and normal glucose tolerance (control, n=1 025). The perinatal outcomes were compared among the five groups. RESULTS: The incidences of macrosomia, large for gestational age (LGA), small for gestational age (SGA), neonatal hypoglycemia and premature birth in the GIGT (1 h) group were significantly higher than those in the control group, but similar to those in the GDM group. The incidences of macrosomia, SGA, neonatal hypoglycemia and premature birth in the GIGT (2-3 h) and the only GCT abnormal groups significantly decreased as compared with those in the GDM group, and similar to those in the control group. GIGT (1 h ) group showed higher incidence of neonatal hypoglycemia and premature birth than the GIGT (2-3 h) and the only GCT abnormal groups. CONCLUSIONS: Different degrees of maternal impaired glucose tolerance have different effects on newborns. As maternal GDM, maternal GIGT (1 h) may increase the risk of macrosomia, LGA, SGA, neonatal hypoglycemia and premature birth.［Chin J Contemp Pediatr, 2009, 11 (3):177-180］