Factors during hospital stay which were different between surviving infants with and without ROP included total number of days of PO2 <50 mmHg, PO2 > 150 mmHg, PCO2 > 80 mmHg, blood gas pH <7.2, days of non-invasive and invasive ventilation support, hospital length of stay, duration of parenteral nutrition, diagnosis of BPD, necrotizing enterocolitis, or sepsis, highest C-reactive protein levels, lowest platelet count, and number of red blood cell transfusions (Table 1). Here, CRP is linked to bronchopulmonary dysplasia.