In univariate analyses , ICU readmission was more common among male subjects ( OR 2.01 ; 95 % CI 1.27-3 .18 ) , infants with grade 3-4 intracranial hemorrhage ( OR 2.13 ; 95 % CI 1.23-3 .69 ) , increasing duration of birth hospitalization ( OR 1.01 per day ; 95 % CI 1.00-1 .02 ) , and prolonged oxygen therapy ( OR 1.01 per day ; 95 % CI 1.00-1 .01 ) .