He finds her puking and gets her to admit that she cheated and is now pregnant.
That brings me to the infant, "mewling and puking in his nurse's arms", who is clearly as vulnerable as it is possible for a visible person to be.
Every child, even whilst "mewling and puking in the nurse's arms," is different, from its very inception, in brains, character, physique and potentiality, from any other child.
Instead, he described it as a "mewling and puking" measure.