Objective: To determine the perinatal and maternal outcome of the macrosomic infants. Study Design: A case-control, retrospective study is performed in the Department of Gynecology and Obstetrics, Istanbul University Cerrahpasa Medical Faculty, between 1988-1992. The maternal and neonatal records of infants with birthweight of at least 4000 g (n = 1000) were reviewed. Another 1000 cases amongst the newborns delivered in the same period between 2500 and 3999 g formed the control group. The obstetrical outcome variables of the groups including mode of delivery and the incidence of maternal and perinatal complications were compared. Results: A total of 16,112 deliveries occurred during the study period. The rate of macrosomic deliveries was 6.21% and the rate of the deliveries (4500 g or heavier) was 1.04%. The mean birthweight of the study group was 4272 +/- 239 and 3277 +/- 316 g of the control group (P < 0.001). While the cesarean section rate was 28.8% for the study group and it was 16.6% for the control group (P < 0.001). In the study group, 17 cases of brachial plexus palsy (2.4%), 16 cases of clavicular fracture (2.3%) and one case of humeral fracture were observed (P < 0.001). The rate of perinatal mortality was 0.8%, in the study group. No perinatal mortality was recorded in the control group. There were 14 cases (1.4%)of asphyxia related to delivery in the study group(P < 0.01). The rate of maternal complications, were significantly higher in the study group (P < 0.01). Conclusion: The macrosomic infants are in increased risk for birth trauma and asphyxia. The risk of birth trauma for the infants weighing 4500 g or more is even greater. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.