How can maternal immunity be transferred to an infant?

• A. Direct exposure after birth
• B. Immunity from mother via placenta or milk
• C. Vaccination after birth
• D. Genetic inheritance

Answer: (B)

Maternal immunity is transferred to the infant through passive immunity, mainly in two ways. First, during pregnancy maternal IgG antibodies cross the placenta and enter the fetal bloodstream, providing systemic protection before birth. Second, after birth, antibodies are delivered via breast milk, especially secretory IgA, which coats the infant’s gut and other mucosal surfaces to help protect against infections in the early months. This passive protection supports the newborn while its own immune system is maturing, and it wanes over time as maternal antibodies decline.

Other options describe different concepts: direct exposure after birth would not transfer maternal antibodies; vaccination after birth helps the infant develop its own active immunity rather than receiving maternal antibodies; and genetic inheritance does not supply specific immunity against pathogens.