The incidence of bronchopulmonary dysplasia ( BPD ) , patent ductus arteriosus , necrotizing enterocolitis , retinopathy of prematurity , and pneumothorax in infants showed no significant differences between the NO and control groups ( P > @ ) , but the incidence of IVH and mortality were significantly lower in the NO group than in the control group ( @ % vs @ % , P < @ ; @ % vs @ % , P < @ ) .