A total of 95 preterm infants, delivered consecutively in a perinatal center, over a 9-month period, were studied serially with real-time ultrasound for detection of subependymal/intraventricular hemorrhage (SEH/IVH); all infants were less than or equal to 32-week gestation and/or less than or equal to 1500 gm birthweight. Detailed statistical analysis was carried out to determine the influence of perinatal factors on the occurrence of SEH/IVH. The incidence of SEH/IVH was 34%; severe hemorrhage (Grade III-IV) occurred in only 13%. Gestational age was an important factor associated with SEH/IVH. Thus, the incidence in infants less than or equal to 29-weeks gestation was 45%, whereas in infants greater than 29-weeks gestation age, it was 19% (p less than 0.01). The overall incidence of SEH/IVH in the group which was less than or equal to 29-weeks gestation and delivered by cesarean section was 53%, whereas in those infants delivered vaginally it was 47%. In infants whose gestational age was less than or equal to 29-weeks, the incidence of hemorrhage was 47% if delivered vaginally and presenting as a vertex and 31% if delivered by cesarean section. In infants greater than 29-weeks gestation, the incidence of SEH/IVH was 42% in those delivered by the vaginal vertex route, 5% if presentation was vertex and delivered by cesarean section (p less than 0.05). In infants greater than 29-weeks gestation, cesarean section in vertex presentation decreased the incidence of SEH/IVH when compared with vaginal vertex delivery.(ABSTRACT TRUNCATED AT 250 WORDS)