A clinical study (including 29 preterm infants with ROP at 33 weeks, 29 non-ROP preterm infants at 33 weeks, and 30 healthy term infants) found that the number of endothelial progenitor cells (p = 0.03) and concentrations of VEGF (p = 0.048), HGF (p = 0.001), and SDF-1 (p = 0.001) were significantly higher in ROP preterm infants than in non-ROP preterm infants. This evidence concerns the gene CXCL12 and retinopathy of prematurity.