The multicenter Italian birth cohort study on incidence and determinants of lower respiratory tract infection hospitalization in infants at 33 weeks GA or more: preliminary results.

BACKGROUND: Respiratory syncytial virus (RSV) causes respiratory infections during the first year of life. Very premature infants have more severe diseases and also 'late preterm infants' may be more susceptible to the infection. AIM OF THE STUDY: To evaluate in an Italian cohort the incidence and risk factors of severe hospitalized lower respiratory tract infection (LRTI) induced or not by RSV during the first year of life.
METHODS: A cohort of 33(+0d)-34(+6d) wGA newborns paired with two sex- and age-matched 35(+0d)-37(+6d) wGA and ≥ 38(+0d) wGA newborns were enrolled. Hospitalization for LRTI induced or not by RSV during the first year of life was assessed through phone interview at the end of the RSV season (November-March) and at the completion of the first year of life. The parents were asked to report hospitalization for any reason.
RESULTS: 1064 neonates were enrolled (November 2009-October 2010), 697 had at least one phone follow-up by September 2010. Babies of 33(+0d)-34(+6d) wGA were more frequently conceived through assisted fertilization technologies, born from cesarean delivery had more frequently acute perinatal risk factors and were more frequently twins. After a mean 6 month-follow-up, we registered 29 hospitalizations for LRTI induced or not by RSV. Hospitalizations were slightly and non-significantly more frequent in 33(+0d)-37(+6d) wGA infants. The risk of hospitalization was significantly 60% reduced in breastfed babies and four folds significantly increased during the RSV season.
CONCLUSION: The very preliminary data of this ongoing study suggest that in 'late-preterm' infants some individual/environmental characteristics of the infants play a relevant role in determining the risk of severe RSV infection.