Serum levels of lysozyme in term and preterm newborns.

Serum lysozyme levels were studied in term babies at the time of delivery and again between 7th and 30th postnatal days, and in preterm babies on the 1st, 3rd, and 5th postnatal days. Levels in term babies at delivery (mean 2.28 mug/ml) were similar to those found in adults, but they fell between the 7th and 30th postnatal days. In premature babies lysozyme levels on the first day of live (mean (0.82 mug/ml) were lower than in term babies. They tended to rise during the first 5 days, by which time they had reached levels found in term babies between the 7th and 30th days. The low lysozyme levels in preterm and in term babies after the first few days of life may contribute to the poor ability of the newborn baby to localize infection and to kill bacteria extracellularly.