Hospitals are changing how they care for premature infants amid growing evidence that some longtime practices, intended to keep the most vulnerable babies alive, may increase risks of serious and potentially deadly complications. Some neonatal intensive-care units are cutting back on the high levels of oxygen traditionally given to premature babies. The change is based on research indicating the high levels may contribute to a condition called retinopathy of prematurity, a leading cause of blindness. Hospitals also are cutting back on prescribing several medications, including antibiotics and anti-reflux drugs, for infants because studies show they confer few benefits and increase risk of adverse reactions. "Everything we do is a balance of risks and benefits for the infant, and we have to be vigilant to make sure we are not making things worse," says Dan L. Ellsbury, director of the Center for Research, Education and Quality at Pediatrix Medical Group, a large neonatal physicians group and a unit of Mednax Inc., of Sunrise, FL. Pediatrix doctors care for some 20% of premature babies receiving intensive care in U.S. hospital NICUs.