Maternal Blood B-Cell (CD19+) Percentages and Serum Immunoglobulin Concentrations Correlate with Breast-feeding Behavior and Serum Prolactin Concentration

PROBLEM: Lactating women recover from pregnancy‐induced immunosuppression while actively secreting immunologically active agents into milk. Few clinical studies have examined changes in postpartum maternal immune status or explored mechanisms. METHOD OF STUDY: We measured blood B‐cell (CD19+) percentages and serum concentrations of immunoglobulin (Ig) G, IgM, and IgA at 1 to 2 weeks, 1 month, and 2 months postpartum in a longitudinal study of seven healthy, lactating women. RESULTS: More frequent or extended breast‐feeding sessions were correlated with lower CD 19+ percentages, reduced serum IgG, and higher serum IgA and IgM concentrations. CD19+ percentages were correlated negatively with serum prolactin concentrations. Blood samples drawn before and 30 min after breast‐feeding did not differ in CD 19+ percentages or serum Ig concentrations. CONCLUSIONS: These findings confirm our previous cross‐sectional study showing a negative correlation between CD 19+ percentages and serum prolactin. Because lactation practices are modifiable, these findings suggest that women can influence the course of lactation‐associated immunologic changes.