The mom who had PKU as a child still has PKU; she hasn't been at much at
risk since she's been an adult and out of her growth phase.  The question
of whether she should stay on a PKU diet while bf is relatively new, since
we didn't used to see PKU babies grow up and have children of their own.  I
would definitely have her consult with the expert on PKU at the state level
(my guess is every state has one), or with one in another state if
necessary, to find out what the available data is.  If I were to make a
decision based on nothing more than common sense, I would strongly urge the
mother to stay on a low-phenylalanine diet while breastfeeding so that the
phenylketones don't pass into her breastmilk in large amounts and cause
retardation in the baby.  I don't know that they would, but I would sure
guess it.

Arly Helm                                       [log in to unmask]
MS, Nutrition; CLE, IBCLC; Lactation Consultant