 Study Question: In infants who are born at gestational ages of 23 07 to 27 67 weeks, does lowering the concentration of supplemental oxygen to target an arterial oxygen saturation by pulse oximetry SpO2of 85-89 compared with 91-95, from the day of birth until the babys first discharge home, increase the probability of survival without severe neurosensory disability to a corrected age of 18 months? 