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 > 0.05 ) , but the incidence of IVH and mortality were significantly lower in the NO group than in the control group ( 7 % vs 17 % , P < 0.05 ; 3 % vs 13 % , P < 0.05 ) .