The pathophysiology of ROP is a two-step process, with the first phase occurring when the preterm infant is born and breathes: The retina becomes hyperoxic and levels of vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF-1) decrease, leading to the cessation of retinal blood vessel growth. This evidence concerns the gene VEGFA and retinopathy of prematurity.