Pathophysiology of retinopathy of prematurity (ROP) still presents a gap. Lately blood tests parameters of premature infants have been measured at different times of ROP, attempting to detect correlations with ROP development and progression. So far, very early post-natal biomarkers, predictive of ROP outcome, have not been detected. Our purpose is to evaluate, in the earliest post birth blood sample, the correlation between routinely dosed blood parameters and ROP outcome. 563 preterm babies, screened according to ROP guidelines, were included and classified in conformity with ET-ROP study in "Group 1" (ROP needing treatment), "Group 2" (ROP spontaneously regressed) and "noROP" group (never developed ROP). The earliest (within an hour after delivery) blood test parameters routinely dosed in each preterm infant were collected. Platelet count was decreased in Group 1 versus noROP group (p = 0.0416) and in Group 2 versus noROP group (p = 0.1093). The difference of thrombocytopenic infants among groups was statistically significant (p = 0.0071). CRP was higher in noROP versus all ROPs (p = 0.0331). First post-natal blood sample revealed a significant thrombocytopenia in ROP needing treatment, suggesting a role of platelets in the pathophysiology and progression of ROP, possibly considering it as a predictive parameter of ROP evolution.