Prolonged Exclusive Breast‐Feeding Results in Low Serum Concentrations of Immunoglobulin G, A and M

Serum levels of IgG, IgA and IgM were measured in 198 infants at ages 2, 4, 6, 9 and 12 months. By age 9 months 30 infants were still exclusively breast-fed; their IgG and IgM levels were significantly lower than those of infants weaned early to formula (before age 3.5 months). By 12 months 6 infants were still exclusively breast-fed; their IgA levels were by then also similarly lower. There was no significant difference in the number of infections experienced by these groups of infants. After 2 months on formula feeding, the IgG and IgM levels of the infants who were exclusively breast-fed for 9 months had caught up with the levels of the infants weaned early to formula. Only at 12 months of age prealbumin levels of the exclusively breast-fed infants showed a positive correlation to IgG and IgA levels; no correlation was found between immunoglobulin levels and levels of serum iron and zinc.