Explanation:

• Immunoglobulin M (IgM), which is found mainly in the blood and lymph fluid, is the first antibody to be made by the body to fight a new infection.
• Immunoglobulin G (IgG), the most abundant type of antibody, is found in all body fluids and protects against bacterial and viral infections.
• IgM is usually produced in response to a pathogen three to seven days after infection. It is not usually transferred from mother to fetus because of its larger structure, which is too big to cross the placenta.
• Researchers suggest that if coronavirus-specific IgM is present at birth, it could either indicate that the infant had produced its own IgM in response to the virus or the mother’s IgM was transferred to the baby through a damaged placenta.It means that IgG antibodies can be transmitted to the foetus through the placenta and appear later than IgM.