Following institutional review board approval and parental informed
consent, medically stable preterm neonates were recruited
from a neonatal intensive care unit. Preterm infants were considered
eligible for recruitment if: a) their gestational age (GA) at birth was between
28 and 32 weeks; b) their birth weight was between 800 and 1400 g; c) their NICU stay at study entry was 15–60 days; and d) their weight at study entry was between 1000 and 1500 g.