Subject characteristics
The clinical characteristics of the preterm infants (Trial flow of study infants.Clinical characteristics of the full-term infants and the preterm infants in the three intervention groups.The data are presented as means (SD) for continuous variables and as numbers (percentage) for categorical variables.The statistical analyses were made a) among the three preterm intervention groups and b) among the full-term and preterm study groups. The variables were analyzed using the χ2 test and Fisher´s exact test for dichotomous and analysis of variance (ANOVA) or Kruskal-Wallis test for continuous variables.*Data informed by the parents.NICU – neonatal intensive care unit.