Abstract
The concentrations of beta-lactoglobulin was measured in the sera of 47 preterm an term neonates during the first few days of life under standardised conditions after feeding with a cows' milk'based formula. Preterm neonates, particularly those of less than 33 weeks' gestation, had higher serum concentrations of beta-lactoglobulin than term neonates given an equivalent mild feed. Prior feeding with breast milk did not diminish the amount of beta-lactoglobulin absorbed. Our results suggest tha te ability of the gastrointestinal tract to exclude antigenically intact food proteins increases with gestational age and that gut closure occurs normally before birth in man.