Serum immunoglobulin levels in normal, premature and postmature newborns and their mothers.

Immunoglobulin (Ig) levels (IgG, IgA, IgM and IgD) were measured in 92 paired maternal and cord sera by the modified single radial immunodiffusion method. There was a progressive increase in mean IgG levels as the gestational age increased which reached a maximum of 1771 mg/100 ml in the postmature babies. The mean IgG level of infants of 32--36 weeks' gestation was lowest (1395 mg/100 ml). The maternal IgG levels were generally higher than those of the cord sera. The mean maternal IgG level (1773 mg/100 ml) was considerably higher than the corresponding level in the cord sera of the lowest gestational age group. Such marked difference was not present in newborns who were of normal gestational ages. The mean IgA and IgM levels of the cord sera were low. There were no significant differences between the mean IgA and IgM levels of newborns in different gestational age groups, even when their mothers showed variations in mean IgA and IgM levels. There was no detectable level of IgD in the cord sera.