Which immunoglobulin is transferred from mother to fetus?

The immunoglobulin that is primarily transferred from mother to fetus is IgG. This transfer occurs during pregnancy, particularly in the third trimester, through the placenta. IgG is the most abundant type of antibody found in the bloodstream, and its ability to cross the placenta makes it crucial for providing passive immunity to the developing fetus. This maternal antibody transfer helps protect the newborn during the early months of life when their immune system is still developing and before they start producing their own antibodies.

IgA, while important for mucosal immunity (found in secretions like breast milk), does not cross the placenta. IgD and IgM also do not transfer effectively to the fetus; IgM, in particular, is primarily produced in response to infections and cannot cross the placenta due to its larger size and structure. Therefore, among the immunoglobulins listed, IgG is the only one that serves the specific function of being transferred from the mother to the fetus, providing critical immunological protection in the early stages of life.