OBJECTIVE: The risk of macrosomia in diabetic complicated pregnancy is increased perinatal morbidity. But it is difficult to predict adverse outcomes after birth with conventional diagnostic tools of diabetes in pregnant women. We evaluated the birth-weight between diabetic and non-diabetic pregnant women based on gestational weeks to determine adverse pregnancy outcome. METHODS: We selected 166 diabetic complicated pregnant women delivered between January 2005 and December 2008 and 248 non-diabetic pregnant women at same period. We compared the birth-weight between two groups in relation to the gestational age below and over 37 weeks. Fetal anomalies, fetal death, and multifetal pregnancy were excluded in this study. And we also evaluated the incidence of baby who had birth-weight 3.8 kg or more and their neonatal outcomes between two groups. RESULTS: There were 4.9% (166/3404) of diabetic complicated pregnancies. The preterm births (birth before 37 weeks of gestation) were occurred 32.5% (54/166) and term births (birth after 37 weeks of gestation) were 67.5% (112/166). The mean birth-weight in preterm birth showed 2,492 g of gestational diabetes, 3,315 g of pregestational diabetes and 2,118 g of control group (P=0.001). The mean birth-weight and gestational age at delivery in term birth showed pregestational diabetes and gestational diabetes were heavier and shorter than those of control group (P=0.002). The incidence of 3.8 kg or more of birth-weighted baby appeared 43.5% (10/23) of pregestional diabetes, 16.8% (24/143) of gestational diabetes and 8.5% (21/248) of control group (P=0.000). The Apgar score less than 7 at minutes of neonate were more frequent in pregestational and gestational diabetes than that of control group (P=0.013). CONCLUSION: It is important to classify the type of diabetes during pregnancy and there should be needed to predict adverse pregnancy outcomes including macrosomia.