SERUM IMMUNOGLOBULIN PATTERNS IN THE FIRST YEAR OF LIFE IN NORMAL AND LOW BIRTH WEIGHT INFANTS: I. RELATIONSHIP TO BIRTH WEIGHT

Serum immunoglobulin levels were measured In mothers and in infants from birth to one year In a longitudinal study of low birth weight infants. The 103 infants were classified into five groups on the basis of 500 gm decrements of birth weight from 3,000 gm to less than 1,500 gm. The mean serum levels of IgG, IgA and IgM in the mothers in the five groups were not significantly different, but there was a significant progression in mean cord serum IgG levels, from 1,312 mg/100 ml In the heaviest Infants to 608 mg/100 ml in the lightest infants. Decay of this IgG acquired from the mother across the placenta proceeded at similar rates in the five groups. Of infants weighing under 2,000 gm, 50% showed a serum IgG level below 200 mg/100 ml between 12 and 24 weeks, with a high incidence of infection. The lightest Infants showed rapid Increases In IgG levels in the first month, the increases correlating with Gram-negative bacterial infections. The mean serum levels of IgG, IgA and IgM at one year were respectively 683, 43 and 57 mg/100 ml.