A multiple logistic regression analysis carried out on the variables found by Student's t-test to be significantly correlated with development of ROP showed that only serum levels of IGF1 in the third week (p = 0.002) and presence of sepsis –considered as clinical, analytical and/or microbiological- in the first three weeks (p = 0.036) significantly increased the probability of developing ROP (Table 3) (Figures 2–4). The gene discussed is IGF1; the disease is retinopathy of prematurity.