Maternal antibody-mediated passive immunity

Maternal antibody-mediated passive immunity refers to the natural process by which mothers confer temporary immune protection to their offspring through the transplacental and breast milk transfer of antibodies. In humans, this primarily involves the active transport of immunoglobulin G (IgG) across the placenta during pregnancy via the neonatal Fc receptor (FcRn), especially during the third trimester. After birth, additional antibodies—mainly secretory IgA—are delivered through colostrum and breast milk, providing local mucosal defense in the infant's gut. This form of immunity protects newborns from various bacterial and viral infections until their own immune system matures enough to generate effective responses. The effectiveness and specificity of transferred antibodies depend on maternal exposure to pathogens or vaccines prior to delivery. While this mechanism offers immediate but short-lived protection—typically lasting up to one year—it can also interfere with an infant’s response to certain vaccinations administered early in life. The presence and subsequent decline (“waning”) of these maternally derived antibodies are important considerations when designing pediatric vaccination schedules. This entry is not a single molecular target such as a receptor or enzyme; rather, it describes an immunological phenomenon involving multiple molecules (primarily IgG) and cellular processes mediated by FcRn receptors on placental cells.

Other names

Maternal passive immunityPassive immunity via maternal antibody transferVertical transfer of maternal antibodiesTransplacental antibody transferBreast milk antibody transfer