The effect of fetal age, birth weight, and sex on cord blood immunoglobulin values.

In order to determine the role played by fetal "factors" in fetal immunoglobulin levels, cord blood samples from 176 normal infants were analyzed for the relationship between immunoglobulin concentration and the gestational age, birth weight, and the sex of the fetus. Cord blood IgM and IgG both increased with gestational age until term, while IgA, its subclasses IgA, and IgA2, and IgD were unaffected by gestational age. IgM and IgG were higher in fetuses weighing 2,000 grams or more, while IgA, IgA, and IgA2 were not influenced by birth weight. Cord blood immunoglobulin values were the same in male and female infants. The interrelationship between cord blood immunoglobulin class and subclass concentrations was examined in two ways: (1) The correlation coefficient r for paired samples was calculated between immunoglobulin concentrations in individual cord sera. (2) Student's test for the mean was used to compare subgroups of the entire sample populations, divided into high, intermediate, and low immunoglobulin values. IgM and IgG, and IgM and IgD were correlated. The data obtained indicate the need to consider the gestational age and birth weight of a neonate in the use of cord blood immunoglobulin values to evaluate the possibility of fetal infection.