As impaired alveolar or microvascular development has been suggested in BPD (9,10), we wanted to extend our previous observations of the correlation between poor postnatal growth and subnormal growth factor levels, both experimentally and in infants, with abnormal angiogenesis and subsequent ROP (16) where we hypothesized that lower postnatal serum concentrations of IGF-I may be a risk factor associated with development of BPD. This evidence concerns the gene IGF1 and bronchopulmonary dysplasia.