Serum immunoglobulin levels and incidence of infection during the first year of life in full-term and preterm infants.

IgG, IgM, and IgA concentrations from birth to 12 months of age, and the incidence of acute infectious processes were determined in 25 full-term and in 26 preterm infants by the single radioimmunodiffusion technique in a prospective study. Infants born at term showed significantly higher IgG levels than preterm babies up to 2 months of age (P less than 0.05) and the frequency of preterm babies with one or more acute infectious episodes during the same period of time was higher, mainly owing to pulmonary, oral mucosa, and ocular infections. The frequency of children with six or seven infectious episodes was also higher in the preterm group (P less than 0.05). IgM and IgA levels did not differ between groups. Even though preterm infants did not show serious bacterial disease or inability to produce antibodies, the incidence of infectious processes was higher in this group up to 2 months of age, a period during which serum IgG levels were lower than in the group of children born at term.