By encouraging mothers, who are the still the primary parent at home, to bond with their baby for a long period of time with the expectation they’ll return to work at the end of the year means the baby will become even more attached to his mother, and separation may become intolerable.

Same goes for the mother. Her attachment to her baby, or her re-thinking of her priorities during this time, may make her even less likely to return to work—thus negating the whole point of the policy, which is to get her attention back on work and off of baby.