Intrauterine infection and cord immunoglobulin M. I. Analysis of methods of assay and levels of immunoglobulin M in normal newborns.

An analysis of methods of assay and levels of immunoglobulin M in the cord serum of 100 normal newborn infants is reported. The geometric mean level of cord IgM was found to be 9.8 mg.%. The 95th percentile value was 19.6 mg.%. IgM levels on day one were not significantly different from cord levels, while by day five a significant increase had occurred (geometric mean 13.6 mg.%). IgA was present in only 3/100 cord sera (in levels above 6.0 mg.%). Any increment of day five IgM over cord levels greater than threefold is thought to be abnormal and this parameter will be further evaluated as an index of neonatal sepsis. Use of locally produced reagents in the IgM assay was found to be more accurate and inexpensive than the commercially available reagents.