More than 30 years ago, the National Institutes of Health sponsored a clinical trial that showed that if premature babies are given oxygen only as needed, the number of infants who develop ROP drops dramatically. Subsequently, hospitals cut back on giving excessive oxygen routinely to premature babies. But, with improvements in neonatal care over the last two decades, the number of babies at risk is increasing as survival rates for smaller premature infants improve. The lower the birth weight, the higher the incidence and severity of ROP.