At the second
At the first the child with congenital violation of all immune system or its partial defeat can be born.
Such children already since the birth continuously are ill.
In the first months of life they need to be surveyed in specialized clinics.
At the second the child is born healthy, however further diseases, mental injuries, any stress can be the cause of defeat of immune system.
Late applying to a breast weakens immunity!
Consider that the newborn has a stress at a separation it from mother right after childbirth, at its late applying to a breast.