Debbie and others,
there is an article in the Journal of the American Dietetic Association
discussing this:
Greve, Linda et el, "Breastfeeding in the management of the Newborn with
Phenylketonuria: A Practical Approach to Dietary Therapy" JADA, March 1994,
Volume 94 Number 3 page 305-309
Good Luck!
Jeannette Newman-Velez, RD, MPH, IBCLC
YWCA WIC PROGRAM
Sacramento, CA