Normal values for mature and immature neutrophils in very preterm babies.

Serial leucocyte counts were made on 24 babies of less than 33 weeks' gestation during the first 5 days of life. The values for mature neutrophils show two important differences from those obtained by previous workers studying term babies, in that the counts were much lower on the first day of life and showed a wider range of values at all ages. In contrast, immature neutrophil counts, expressed either as absolute values or as a proportion of the total neutrophil count (the I/T ratio), were similar to those found in previous studies and had a considerably narrower range.