It is well recognised that the primaryimmunoglobulin (Ig) of the newborn is the maternal IgG as this is the only Ig to cross the placental barrier. On the other hand, it is IgM which is synthesized by the newborn in the early postnatal period followed by IgA and IgG.
The IgG from the mother protects the baby from many infections in the first months of life. Thenewborn baby may get additional antibody via breast feeding, but this antibody does not get absorbed from the baby's gastrointestinal tract.