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Managing your Baby’s PKU

Managing your baby's PKU can be challenging and initially there will be many things you need to learn and understand. Your dietitian and others who have been through the same experiences will be a great support to you during this time.

From Birth to Six Months

Breast milk is the ideal food for babies, as it contains all the nutrients required to support growth and development.

If your baby is diagnosed with PKU your dietitian will work closely with you to introduce a Phenylalanine (Phe)-free formula for infants, alongside breast milk or standard infant formula.  They need this because a baby with PKU cannot tolerate full quantities of breast milk/standard infant formula and keep their Phe levels within the desired range.

At diagnosis it may be necessary to stop breastfeeding or giving your baby their standard infant formula for up to a few days to help reduce Phe levels. This can be stressful as it may occur at a time when breastfeeding is just being established. If you wish to continue breastfeeding, it is important to maintain your supply so that you can resume breastfeeding as soon as possible. Your metabolic healthcare professional team will give you advice about how to maintain your supply by expressing milk.

As your baby will have less breast milk or standard infant formula, the PKU formula will also provide the additional Phe-free protein, vitamins, minerals and energy your child needs to grow. Your baby will be closely monitored over their first few months and years of life to manage their Phe levels in their blood. It is natural to be worried and concerned but remember that you are not alone. Your metabolic healthcare professional team will provide lots of support and there are other families out there going through the same experiences as you.

Why does my baby need to take a PKU (Phe-Free) formula?

Taking PKU formula helps to lower blood Phe levels while making sure they have sufficient amounts of protein for growth and development.   The balance of breast milk/standard infant formula and PKU formula ensures your baby has enough protein, energy and nutrients while keeping their Phe levels within the acceptable range.

How much milk should I give my baby?

The balance of breast milk/standard infant formula and your baby’s PKU formula helps keep blood Phe levels steady. Your dietitian will let you know how much of each milk to have to keep your baby’s blood Phe level at the optimal level as your baby grows. This will change depending on the blood Phe level and can change weekly at times. That is why frequent monitoring is required.

Reference source:

PKU Handbook [2005]. Australasian Society for Inborn Errors of Metabolism (ASIEM) (Australia and New Zealand). Chapter 3: Feeding your baby

What can affect my baby’s Phe levels?

Monitoring your baby’s blood Phe levels is an important part of managing PKU. Good control will lead to optimal growth and development and your doctor and dietitian will help and support you with this.  It is normal for a baby’s Phe levels to sometimes fluctuate due to periods of rapid growth or illness. However if your baby eats the prescribed amount of protein and takes the prescribed amount of  PKU supplement or PKU formula spread through the day, this can help minimise any ups and downs.

What should I do if my baby is ill?

If a baby is sick, has an infection or has lost their appetite, their body breaks down its own protein to use as energy. This releases Phe into the blood. To help minimise this encourage your baby to drink plenty of fluids including their PKU formula. Contact your GP or metabolic team for advice when this happens.  Levels will return to normal once your baby is well again.

Please Note: The dietary treatment for PKU varies for each person so all information presented here is for guidance only. Your own dietitian and/or doctor will advise you on all aspects relating to management of PKU for you and your family.