Lisa, I know other PKU women who have had babies, breastfed them, and it has worked out. I would definitely encourage your friend to continue! Has she spoken with her PKU specialist to see if they have seen other PKU women with babies go threw this same thing? I’m not so sure if this is PKU related. My mom works as a labor doula/birth educator (and she has 8 kids) so she knows a bit about babies. When my sister, whose now 5 months was born my mom had TONS of issues with breastfeeding her and she cried alot. Although my sister does have PKU, my mom does not so the reason my sister was having a hard time couldn’t be caused by the milk not having enough protein. My mom said she has seen a lot of new mothers have trouble with babies breastfeeding due to what’s called nipple confusion. From what my mom told me nipple confusion is when the baby uses a sucking technique that is used for drinking out of a bottle, while they’re breastfeeding and this makes it difficult to get any milk out. This can be caused by giving the baby bottles or pacifiers before they are approx 2-4 weeks and have gotten the hang of breastfeeding. Is your friend giving the baby pacifiers? I would suggest your friend not switch to bottles because that could cause more confusion if it is nipple confusion. It probably has nothing to do with PKU and is just one of those things that happens. Good luck to your friend! Just keep encouraging her!