How did my baby get PKU?

We all inherit genes in pairs, one from our mother and one from our father. Both you and your partner are carriers of the PKU gene. As carriers you do not have PKU because you have one working PKU gene and one non-working PKU gene but when both parents are carriers there is a one in four chance their baby will have PKU.

Was there anything I could have done to prevent my baby having PKU?

No, there was nothing you did or could have done.

Will my baby grow out of PKU?

No, PKU is an inherited metabolic condition.

What is the treatment for PKU?

PKU is treated with a very low phenylalanine diet. Phenylalanine is found in all protein containing foods such as meat, fish, cheese, bread and potatoes and is essential for growth and functioning. Phenylalanine can’t be completely removed from the diet so it is restricted and given in small, measured or weighed amounts each day. The amount given is individual for each baby and your dietitian will advise. The low phenylalanine diet is supplemented with a special protein formula that does not contain any phenylalanine. The special protein formula is called a protein substitute and is given at each feed to start with and then as your baby grows it will be given at least three times a day. When your child grows older your dietitian will advise you about the next stage of the diet. PKU requires lifelong treatment.

Will my baby develop normally?

Yes, they should grow and develop as expected provided they follow the diet as recommended by their dietitian. People with PKU typically have the same educational and career goals as other people who do not have PKU.

Will I still be able to breastfeed my baby?

Yes. Your baby can be fed directly from the breast provided a measured amount of the protein substitute is given before each breastfeed. The protein substitute will help limit the amount of breast milk taken by your baby and thereby lower the phenylalanine intake. Your dietitian will give guidance and help. Alternatively, a small measured amount of regular infant formula may be given in a bottle as well as the protein substitute (in a separate bottle). With support, both methods of feeding a baby with PKU are successful. Babies with PKU will grow and develop well whether they are breast or bottle fed, it is your choice and what works best for you and your baby.

The low phenylalanine diet sounds complicated. How can I make it work?

The diet does require considerable effort but with the expertise and support of your dietitian; planning and organising along with the range of foods available both on prescription and in the supermarket you will soon begin to manage it successfully. Making the diet work is a team effort. Keeping a positive attitude and accepting help from grandparents and family will help lighten the load.

What would happen if my baby had too much phenylalanine in their diet (high phenylalanine levels)?

High phenylalanine levels are usually caused by: -

  • Eating too much protein containing foods
  • Illness
  • Not having enough protein substitute
  • Lack of calories.

Your dietitian will advise you how to get the phenylalanine levels back in the safe bracket and how to keep the levels consistently in the safe range.

What would happen if my baby accidentally ate the wrong food?

If this happens your baby’s phenylalanine levels are likely to be high (out of the safe bracket). No lasting harm will occur but you should be aware that continual high blood phenylalanine levels will cause harm. It is important to work with your hospital team to keep your child developing well.

How long do phenylalanine levels have to be high to damage my baby?

There is no definite time but frequent and prolonged high levels should be avoided to protect the brain from harm.

How do I monitor my baby’s phenylalanine levels?

You will be shown by your metabolic team, usually a metabolic nurse specialist, how to take the blood spots from your baby’s heel. The blood spots you take (at home) will be posted to the same lab that carried out your baby’s newborn screening. Your dietitian will contact you with the result and adjust your baby’s diet according to the level of phenylalanine in their blood.

When my baby is an adult and wants to have children will they also have PKU?

The chance of your baby with PKU also having a baby with PKU is approximately 1 in 100. For women with PKU there are additional dietary measures prior to and during pregnancy as high phenylalanine levels during pregnancy can restrict the development of the unborn baby.

I have a brother/sister, if they have children will they have PKU?

It is possible that any brothers or sisters you have may also carry the non-working PKU gene and their partner would have to be a carrier too (1 in 50 of the population) and then the likelihood that any children they have also having PKU is 1 in 400.