Perinatal morbidity and mortality are known to be higher for the macrosomic neonate whose birth weight is 4500 g or more, compared with that of appropriate-weight term-size neonates. In a retrospective study comparing 287 macrosomic neonates with 284 appropriate-weight term-size neonates, we found that macrosomia occurred in 1.3% of our annual deliveries, with a male-to-female ratio of 2.3:1. Factors that occurred significantly more frequently in the mothers of macrosomic infants were maternal obesity, multiparity, diabetes mellitus, and previous delivery of an infant heavier than 4000 g. During the intrapartum period the incidence of labor augmentation by oxytocin, shoulder dystocia, and cesarean section was significantly greater in fetal macrosomia. Most significantly, this study revealed that macrosomia. Most significantly, this study revealed that macrosomic fetuses do not experience greater fetal distress in biophysically monitored labor than appropriate-weight term-size fetuses. Twenty-nine (10%) of the macrosomic infants required admission to the neonatal intensive care unit (NICU) compared to 9 (3%) of the control patients (P less than 0.01). This excess neonatal morbidity in the macrosomic neonates was predominantly caused by the delivery process.