The Phenobarbital Prophylaxis for Neonatal Intracranial Hemorrhage Study was a clinical trial supported by the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS), and enrolled 280 infants at three Harvard Neonatal Intensive Care Units between June 1981 and April 1984. Babies were recruited for the study if their birth weights were 1,750 grams or less, they had no demonstrable intraventricular hemorrhage by cranial ultrasound and they required intubation within the first twelve hours of life. Data collected included maternal history, infant health status, and events of hospitalization.