This cohort was established to evaluate the risk factors for hospitalization during the first year of life in children born at different gestational ages. The cohort included over 2,300 consecutive newborns born between across 30 neonatology units in hospitals across Italy from November 2009 to December 2012. For each enrolled newborn of 33 to 34 weeks gestational age (wGA), two further newborns of the same sex and with the nearest date of birth were enrolled: one of 35 to 37 wGA and one of greater than 37 wGA. Data was first collected by enrolling physicians within two days after birth, with subsequent structured phone interviews at the end of the epidemic Respiratory Syncytial Virus (RSV) season (end of March in Italy) and at 12 months of age.