If you have phenylketonuria (PKU) and you're pregnant, you're probably wondering what changes you'll need to make to ensure a healthy start for your little one. Here's everything moms with PKU need to know.
What is phenylketonuria (PKU)?
PKU is a genetic condition in which your body is missing a special enzyme. This enzyme works to protect against the dangerous build-up in your body of the amino acid phenylalanine. When a woman with PKU gets pregnant, her condition is referred to as maternal PKU.
Happily, with a little bit of planning and strict adherence to a low-phenylalanine diet, you can have a healthy pregnancy with maternal PKU.
What is a safe diet if you have phenylketonuria (PKU)?
If you have maternal PKU, you likely know all about the special diet for the condition — even if you've been off it for a while.
The low-phenylalanine diet involves drinking a phenylalanine-free medical protein formula and eating precisely measured amounts of fruits, vegetables, bread and pasta. The diet also eliminates all high-protein foods, including meat, poultry, fish, dairy products, eggs, beans and nuts.
And, of course, all foods sweetened with aspartame (Equal or NutraSweet) are absolutely off-limits, as the sweetener contains high levels of phenylalanine.
The diet definitely isn't easy to follow. But for pregnant women with PKU, it's absolutely necessary. Not sticking to it while you're pregnant can put your baby at great risk for a number of health problems, including serious mental deficits.
There's no doubt that it will be tough to go back on the diet, especially if you've been off it for many years (not to mention stick with it when pregnancy cravings have you hankering for off-limits foods). But the benefits to your developing baby will be well worth the effort.
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Ideally, you'll resume the diet at least three months before conception.[1] That way, you can ensure that your blood levels of phenylalanine are kept low throughout your entire pregnancy.
If your pregnancy is unplanned, you'll want to get back on a low-phenylalanine diet and start drinking the formula as soon as possible. Even starting the diet early in pregnancy will reduce the potential for serious developmental delays or birth defects in children of mothers with PKU.
If you find yourself slipping off the diet or have trouble getting started, it might help to get some professional help from a counselor who is familiar with your condition. A support group of other mothers with PKU may be helpful too. For more information, try the website for the National PKU Alliance.
What are the risks of unmanaged maternal PKU to a baby?
Having too much phenylalanine in your blood can create serious health consequences for your baby.
Unmanaged maternal PKU can put your unborn child at risk of intellectual disabilities, abnormal brain development, developmental delays, small head size (microcephaly), heart problems and low birth weight.
Will I need any special monitoring during pregnancy if I have PKU?
Experts recommend tight supervision for moms-to-be with PKU. This close monitoring likely will include regular visits with the doctor who treats your PKU and twice-weekly blood tests to look at phenylalanine levels and make sure they aren't rising to unsafe levels.[2]
You may also have more visits to your obstetrician — with more frequent ultrasounds and tests of fetal well-being to monitor the health and growth of your baby — than other expectant mothers.
If I have maternal PKU, will my baby also have PKU?
Not necessarily. PKU is a genetic condition. But it follows a pattern of autosomal recessive inheritance, which means a child needs two copies of an altered gene — one from each parent — for the condition to take hold.
If you have maternal PKU and your partner is a PKU carrier (meaning that he has one copy of the altered gene instead of two), there's a chance your child will also have PKU. If your partner is not a PKU carrier (even if you have maternal PKU), there's no chance your baby can inherit the condition. A genetic counselor can help you understand your chances of passing PKU to your little one.
Though the potential risks of uncontrolled maternal PKU sound scary, the good news is that with the proper treatment, diet and medical supervision, you can have a perfectly healthy pregnancy and baby.
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