Regarding biological markers outside the normal range, elevated levels of C-reactive protein (CRP) (OR = 1.66, 95% CI 1.03–5.39, p = 0.001) and Interleukin-6 (IL-6) (OR = 2.26, 95% CI 1.36–6.15, p < 0.001) were both significantly associated with an increased risk of developing ROP stage 2 or above. This evidence concerns the gene IL6 and retinopathy of prematurity.