Immunoglobulin profile of the preterm baby.

Immunoglobulin concentrations were determined in 64 consecutively born preterm babies at birth and serially throughout each baby's stay in the neonatal unit. No significant IgG generation was found during the first 15 weeks of life, regression analysis giving an exponential decay model. Concentrations fell to 2 g/l or less in 10 (16%) babies (gestational age 25 to 32 weeks), and were as low as 1 g/l in four babies (gestational age 25 to 29 weeks). The effects of gestational age and birthweight on the concentration of IgG at birth were highly interdependent and significant. Most babies had no detectable IgA at birth, and no effect of gestational age or birthweight, or both, on either initial IgA or IgM concentrations could be shown.