Intrauterine growth retardation (less than -2.5SD)

Infants with chronic lung disease (CLD) or other respiratory disease

Infants received mechanical ventilation.

Infants with chronic heart disease (CHD) or congenital anomaly (such as immunodeficiency).

Infants received less than 3 doses of palivizumab during the first 6 months of life

Effect of Palivizumab on Later Recurrent Wheezing in Preterm Infants