The American College of Obstetricians and Gynecologists' "Guidelines for vaginal delivery after a previous cesarean birth" include a precautionary statement regarding estimated fetal weight of more than 4000 g. To evaluate the validity of this restriction, we conducted an analysis of the outcomes of 301 trials of labor with birth weights equal to or greater than 4000 g. In the birth-weight range of 4000-4499 g, 139 of 240 patients (58%) delivered vaginally. In the group with birth weights exceeding 4500 g, 26 of 61 patients (43%) delivered vaginally. When compared with 1475 trials of labor with birth weights under 4000 g, no significant differences in perinatal or maternal morbidity were found. Comparison with a control group of 301 women with no previous uterine surgery who delivered macrosomic infants also demonstrated no significant differences in perinatal or maternal morbidity. The medical literature does not support elective cesarean section for suspected fetal macrosomia in nondiabetic women, and based on our experience, there appears to be no reason for treating previous-cesarean mothers differently.