4.2. Clinical Features

The clinical features that might be related to ROP development were recorded, including gender, BW (grams), GA (weeks), mode of delivery, Apgar score at the 1st and 5th minute, duration of ventilation support (days), birth asphyxia (determined as Apgar score less than 6 at the 10th minute and pH < 7.0 or blood base excess [BE] < −15 mmol/L in cord blood), intrauterine infection (confirmed by a positive culture in originally sterile samples combined with clinical symptoms or the development of pneumonia within the initial 48 h after birth), late-onset infection (comprising pneumonia, sepsis or urinary tract infections) and prematurity-related complications such as BPD, IVH and NEC.