Which Immunoglobulin provides natural passive immunity through the placenta to a newborn?

IgG In humans, maternal antibodies (MatAb) are passed through the placenta to the fetus by the FcRn receptor on placental cells. This occurs predominately during the third trimester of pregnancy and thus is often reduced in babies born prematurely. Immunoglobulin (IgG) is the only antibody isotype that can pass through the human placenta, and is the most common antibody of the five types of antibodies found in the body. IgG antibodies protect against bacterial and viral infections in fetuses