Which type of immunity would most likely be present in a newborn due to maternal antibodies transferred across the placenta?

• A. Innate immunity
• B. None
• C. Acquired active immunity
• D. Acquired passive immunity

Answer: (D)

Newborn protection from antibodies carried by the mother is a form of passive immunity. Maternal IgG antibodies cross the placenta during pregnancy and provide systemic protection to the infant after birth. Because the infant isn't making these antibodies themselves, this is acquired passive immunity. It’s a temporary boost—maternal antibodies later wane as the baby’s own immune system matures and begins producing its own antibodies in response to infections or vaccines. Innate immunity is present at birth but does not involve antibodies transferred from the mother, and acquired active immunity would require the newborn to generate its own antibodies after exposure.