PKU (Phenylketonuria) in your baby
Phenylketonuria (also called PKU) is a condition in which your body can’t break down an amino acid called phenylalanine. Amino acids help build protein in your body. Without treatment, phenylalanine builds up in the blood and causes health problems.
In the United States, about 1 in 10,000 to 15,000 babies is born with PKU each year. The illness happens in all ethnic groups. But it’s more common in people who are Native American and Northern European than those who are African-American, Ashkenazi Jewish or Japanese.
PKU is inherited. This means it’s passed from parent to child through genes. A gene is a part of your body’s cells that stores instructions for the way your body grows and works. Genes come in pairs—you get one of each pair from each parent.
Sometimes the instructions in genes change. This is called a gene change or a mutation. Parents can pass gene changes to their children. Sometimes a gene change can cause a gene to not work correctly. Sometimes it can cause birth defects or other health conditions. A birth defect is a health condition that is present in a baby at birth.
Your baby has to inherit a gene change for PKU from both parents to have PKU. If she inherits the gene from just one parent, she has the gene change for PKU, but she doesn’t have PKU. When this happens, your baby is called a PKU carrier. A PKU carrier has the gene change but doesn’t have PKU.
All babies have a newborn screening test for PKU. Newborn screening checks for serious but rare conditions at birth. It includes blood, hearing and heart screening. With newborn screening, PKU can be found and treated early so babies can grow up healthy.
Before your baby leaves the hospital, his health care provider takes a few drops of blood from his heel. The blood is collected on a special paper and sent to a lab for testing. The lab then sends the results back to your baby’s provider.
If newborn screening results aren’t normal, it simply means your baby needs more testing. Your baby’s provider can recommend another kind of test, called a diagnostic test. This test can check to see if your baby has PKU or if there is some other cause for abnormal test results.
If your baby is tested before he’s a full day old, it’s possible for the test to miss PKU. Some experts recommend that if your baby was tested within the first 24 hours of life, he should be tested again at 1 to 2 weeks of age.
Babies born with PKU seem normal for the first few months of life. But without treatment, they begin to have signs and symptoms of the illness at about 6 months of age. These include:
- Jerky movements in arms and legs
- Lighter skin and eyes (Babies with PKU can’t properly make melanin, the pigment in the body that’s responsible for skin and hair color.)
- Musty body smell
- Skin rashes
- Small head size
- Taking longer than expected to sit, crawl or walk
- Losing interest in surroundings
- Delays in mental and social skills
- Intellectual disabilities
- Behavior problems, like being hyperactive
If your baby has PKU, he may need testing as often as once a week or more often for the first year of life to check his phenylalanine levels. After that, he may have testing once or twice a month throughout childhood.
Your baby needs to follow a special meal plan that is low in phenylalanine. It’s best to start this meal plan as soon as possible, ideally within the first 7 to 10 days of life.
At first, your baby gets a special protein formula that has reduced phenylalanine. Protein is important to help your baby grow and develop. The amount of phenylalanine in the formula is controlled to meet you baby’s individual needs. Your baby also can have some breast milk. Your breast milk has phenylalanine in it, so talk to your baby’s provider to find out how much breast milk your baby can have.
When your baby is ready to eat solid foods, she can eat vegetables, fruits, some grains (like low-protein cereals, breads and pasta) and other low-phenylalanine foods. If your baby has PKU, she should not eat:
- Milk, cheese, ice cream and other dairy products
- Meat and poultry
- Food or drinks that contain aspartame. This is an artificial sweetener that has lots of phenylalanine in it. It’s sold as NutraSweet® and Equal®.
PKU meal plans are different for each baby and can vary over time depending on how much phenylalanine your baby can take. Health care providers at a medical center or clinic that has a special program to treat PKU can help you create a PKU meal plan for your baby. Ask your baby’s health care provider for information on a medical center or clinic that treats PKU.
Your child follows the PKU meal plan through her whole life. If she eventually gets pregnant, she follows her meal plan throughout pregnancy. Most pregnant women who have PKU can have healthy pregnancies and healthy babies.
The medicine Kuvan® (sapropterin dihydrochloride) can help some people with PKU. The medicine is more likely to work in people with mild or special forms of PKU. Children who take Kuvan® must follow a special meal plan, but it may not be as strict as one for those not taking the drug. They still need regular blood tests to check phenylalanine levels.
National PKU News
Serum phenylalanine screening
Genetics Home Reference: PKU
Last reviewed February 2013
See also: Genetic counseling, Newborn screening
Frequently Asked Questions
Can dad's exposure to chemicals harm his future kids?
Dad's exposure to harmful chemicals and substances before conception or during his partner's pregnancy can affect his children. Harmful exposures can include drugs (prescription, over-the-counter and illegal drugs), alcohol, cigarettes, cigarette smoke, chemotherapy and radiation. They also include exposure to lead, mercury and pesticides.
Unlike mom's exposures, dad's exposures do not appear to cause birth defects. They can, however, damage a man's sperm quality, causing fertility problems and miscarriage. Some exposures may cause genetic changes in sperm that may increase the risk of childhood cancer. Cancer treatments, like chemotherapy and radiation, can seriously alter sperm, at least for a few months post treatment. Some men choose to bank their sperm to preserve its integrity before they receive treatment. If you have a question about a specific exposure, contact the Organization of Teratology Information Specialists at www.otispregnancy.org.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
Does cleft lip or cleft palate cause dental problems?
A cleft lip or cleft palate that extends into the upper gums (where top teeth develop) can cause your baby to have certain dental problems, including:
- Missing teeth
- Too many teeth
- Oddly shaped teeth
- Teeth that are out of position around the cleft
Every baby with a cleft lip or palate should get regular dental checkups by a dentist with experience taking care of children with oral clefts. Dental problems caused by cleft lip or palate usually can be fixed. If needed, your baby can get ongoing care by a team of experts, including:
- A dentist
- An orthodontist to move teeth using braces
- An oral surgeon to reposition parts of the upper jaw, if needed, and to fix the cleft
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause ear problems?
Cleft lip does not cause ear problems.
Babies with cleft palate, however, are more likely than other babies to have ear infections and, in some cases, hearing loss. This is because cleft palate can cause fluid to build up in your baby’s middle ear. The fluid can become infected and cause fever and earache. If fluid keeps building up with or without infection, it can cause mild to moderate hearing loss.
Without treatment , hearing loss can affect your baby’s language development and may become permanent.
With the right care, this kind of hearing loss is usually temporary. Your baby’s provider may recommend:
- Having your baby’s ears checked regularly for fluid buildup
- Medicines for treating fluid buildup and ear infections
- Ear tubes if your baby has fluid in his ears over and over again. Ear tubes are tiny tubes that are inserted into the eardrum to drain the fluid and help prevent infections.
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause problems with breastfeeding?
Babies with only a cleft lip usually don’t have trouble breastfeeding. Most of the time, they can breastfeed just fine. But they may need some extra time to get started.
Babies with cleft lip and palate or with isolated cleft palate can have:
- Trouble sucking strong enough to draw milk through a nipple
- Problems with gagging or choking
- Problems with milk coming through the nose while feeding
Most babies with cleft palate can’t feed from the breast. If your baby has cleft palate, he can still get the health benefits of breastfeeding if you feed him breast milk from a bottle. Your provider can show you how to express (pump) milk from your breasts and store breast milk.
Your baby’s provider can help you start good breastfeeding habits right after your baby is born. She may recommend:
- Special nipples and bottles that can make feeding breast milk from a bottle easier
- An obturator. This is a small plastic plate that fits into the roof of your baby’s mouth and covers the cleft opening during feeding.
See also: Cleft lip and cleft palate, Breastfeeding
Does cleft lip or cleft palate cause speech problems?
Children with cleft lip generally have normal speech. Children with cleft lip and palate or isolated cleft palate may:
- Develop speech more slowly
- Have a nasal sound when speaking
- Have trouble making certain sounds
Most children can develop normal speech after having cleft palate repair. However, some children may need speech therapy to help develop normal speech.
See also: Cleft lip and cleft palate
What are choroid plexus cysts?
The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.
What if I didn't take folic acid before pregnancy?
If you didn’t take folic acid before getting pregnant, it doesn't necessarily mean that your baby will be born with birth defects. If women of childbearing age take 400 micrograms of folic acid every day before and during early pregnancy, it may help reduce their baby’s risk for birth defects of the brain and spin called neural tube defects (NTDs). But it only works if you take it before getting pregnant and during the first few weeks of pregnancy, often before you may even know you’re pregnant.
Because nearly half of all pregnancies in the United States are unplanned, it's important that all women of childbearing age (even if they're not trying to get pregnant) get at least 400 micrograms of folic acid every day. Take a multivitamin with folic acid before pregnancy. During pregnancy, switch to a prenatal vitamin, which should have 600 micrograms of folic acid.
Last reviewed November 2012