Moreover, ROP severity is correlated to IGF-I serum concentrations and duration of low IGF-I concentrations.7, 37 The reduced growth rates at a PMA of around 30 weeks could be biologically related to initiation of phase II of ROP development, which has been demonstrated to correlate to an increase of the initially low levels of IGF-I.7 Lower IGF-I levels in the first postnatal weeks are also associated with BPD among very preterm infants.17 It is reasonable to postulate that factors that control somatic growth also influence retina and lung development. Here, IGF1 is linked to bronchopulmonary dysplasia.