Immunity being passed to baby. Computer illustration showing how some of the antibody-mediated immunity (coloured dots) gained by a mother through exposure to pathogens (right) during her lifetime, is passed to her unborn child during pregnancy (lower left). This form of immunity is known as maternal passive immunity. It is a form of naturally acquired passive immunity that occurs around the third month of pregnancy, whereby maternal antibodies (MatAb) are passed through the placenta to the foetus.