Serum immunoglobulins in the first year of life.

Serum IgG, IgM, and IgA were measured in 316 infants younger than 12 months of age. Information including the child's race, sex, age, and past history of infections or atopy was collected. Birth records were also reviewed to ascertain the child's birthweight and gestational age. Serum IgG levels were higher in black infants than in white infants after the age of 4 months. Serum IgM levels were higher in black females than in black males for infants older than 1 month. For infants younger than 4 months of age, those weighing less than 2500 g at birth had lower IgG levels than those weighing more than 2500 g. Infants younger than 1 month whose gestational age had been less than 36 weeks had lower IgG levels than those greater than 36 weeks. Infants aged 1 to 4 months whose gestational age had been less than 36 weeks had lower IgG levels than did those 40 or more weeks. Infants with a positive history for atopy had lower IgG levels than similarly aged infants with a negative history.