The present invention relates to a composition comprising Insulin Growth Factor I (IGF-I) or an analog thereof in combination with Insulin Growth Factor Binding Protein (IGFBP) or an analog thereof, said combination having a molar ratio of IGF-I to IGFBP 5 being lower than equimolar, preferably in the range from 1:20 to 1:3.33, for use in the treatment of a patient suffering from complications of preterm birth, very preterm birth and/or extremely preterm birth, as well as a method for treating a patient suffering from complications of preterm birth, very preterm birth and/or extremely preterm birth.