Kuvan is a medication recently approved by the FDA in the US to treat PKU. Not all PKUers respond, as it boosts what ability a PKUer has to digest phe. If you have classic PKU it is less likely to work, as you may have less residual enzyme activity. I have variant (or moderate) PKU and respond well. As for going on the diet – you need to have your levels checked. The previous poster said she didn’t need to go on the diet during pregnancy as her levels were fine. That’s ok IF your levels are below 6 off-diet. If not, you NEED to be on-diet to prevent possible birth defects.