The PKU Diet and Pregnancy

The PKU Diet and Pregnancy

At Salford’s PKU day in May 2019, Diane Green took attendees through The PKU Diet & Pregnancy, providing information on how pregnant women with PKU can adapt their low protein diet to ensure their baby is born both happy and healthy.

The effects of blood phenylalanine on the offspring of women with phenylketonuria (PKU) were recognised in the late 1950s and 1960s. PKU mums require access to PKU diet protein substitutes, low protein foods and calorie supplements. During pregnancy, PKU mums also require Folic acid, vitamin D and EFA supplementation as per NICE guidance. Your dietitian can provide tailored advice for you.

Maternal PKU: A brief history

A 1957 study found that high phe levels in pregnant mothers, can produce foetal brain damage, and the research today sings from the same hymn sheet.

The importance of maintaining an even stricter PKU diet during pregnancy can’t be stressed enough amongst dietitians and consultants specialising in the dietary management of PKU.

From 1984-2002, the first Maternal PKU collaborative study took place. This study involved 416 pregnancies and monitored the Phe levels in PKU patients as well as the development of their new-borns into childhood.

Maternal PKU syndrome

Phe blood levels consistently over 360, have been found to contribute to Maternal PKU Syndrome, which can cause an unborn child to suffer from:

• Intellectual disability
• Low birth weight
• Microcephaly
• Congenital heart defects
• Miscarriage
• Facial dysmorphia
• And more.

Can pregnant mothers restrict themselves too much?

In a few cases, expectant mothers have been so keen to stay on their low protein diet, that they have gone too far in restricting protein and their baby has been born malnourished.

The baby still needs the building blocks of protein to grow into a healthy child, and protein substitutes or amino acid formulas can help facilitate that, as well as other supplements as recommended by your dietitian.

Unplanned pregnancies

For unplanned pregnancies, phe levels need to be brought into range as soon as possible to minimise the unborn child’s potential health issues. It is strongly advised that if you are living with PKU, you use multiple forms of contraception, to avoid potential harm.

Target Phe levels during pregnancy

European guidelines stipulate that Phe levels should be maintained in the range of 120-360 micromol/L throughout pregnancy to ensure your baby is born both happy and healthy.

Always consult your dietitian if you are thinking about having a child, to ensure the best outcome for your family and have the best guidance for your PKU diet.