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.