In contrast, when the concentration of TNF-α was in the top quartile, the risk of ROP was significantly elevated only when the concentrations of IGF-1, IGFBP-1, VEGF, VEGFR-1, VEGFR-2, ANG-1, ANG-2, or PIGF were not in the top quartile. This evidence concerns the gene PIGF and retinopathy of prematurity.