BACKGROUND: Infants delivered by vacuum extraction or other operative techniques may be more likely to sustain major injuries than those delivered spontaneously, but the extent of the risk is unknown. METHODS: From a California data base, we identified 583,340 live-born singleton infants born to nulliparous women between 1992 and 1994 and weighing between 2500 and 4000 g. One third of the infants were delivered by operative techniques. We evaluated the relation between the mode of delivery and morbidity in the infants. RESULTS: Intracranial hemorrhage occurred in 1 of 860 infants delivered by vacuum extraction, 1 of 664 delivered with the use of forceps, 1 of 907 delivered by cesarean section during labor, 1 of 2750 delivered by cesarean section with no labor, and 1 of 1900 delivered spontaneously. As compared with the infants delivered spontaneously, those delivered by vacuum extraction had a significantly higher rate of subdural or cerebral hemorrhage (odds ratio, 2.7; 95 percent confidence interval, 1.9 to 3.9), as did the infants delivered with the use of forceps (odds ratio, 3.4; 95 percent confidence interval, 1.9 to 5.9) or cesarean section during labor (odds ratio, 2.5; 95 percent confidence interval, 1.8 to 3.4), but the rate of subdural or cerebral hemorrhage associated with vacuum extraction did not differ significantly from that associated with forceps use (odds ratio for the comparison with vacuum extraction, 1.2; 95 percent confidence interval, 0.7 to 2.2) or cesarean section during labor (odds ratio, 0.9; 95 percent confidence interval, 0.6 to 1.4). CONCLUSIONS: The rate of intracranial hemorrhage is higher among infants delivered by vacuum extraction, forceps, or cesarean section during labor than among infants delivered spontaneously, but the rate among infants delivered by cesarean section before labor is not higher, suggesting that the common risk factor for hemorrhage is abnormal labor.