The rate of hemolysis of transfused adult red blood cells in the prema
ture circulation may be higher than in the native circulation and prod
uce a significant bilirubin load on the immature liver during the firs
t days of life with consequent hyperbilirubinemia. The association bet
ween the transfusion of packed red blood cells and consequent change o
f serum bilirubin level was evaluated in 35 premature infants with bir
th weight of <1,250 g during the first 10 days of life, using the anal
ysis of variance method. There was a significant increase of bilirubin
level with a mean of 24.3 mu mol/l following packed red blood cells t
ransfusion. Birth weight had a significant negative effect and mechani
cal ventilation for >2 days had a significant positive effect on bilir
ubin levels; however, the changes were of small magnitude. The results
of our study indicate that a rise of bilirubin level following blood
transfusion to very low birth weight infants during the early neonatal
period should be anticipated.