Cystic fibrosis

Newborn screening for cystic fibrosis is done using a small amount of blood collected from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.

During screening, a special machine measures how much of a certain substance (called immunoreactive trypsinogen or IRT) is in your baby’s blood. IRT is made in the pancreas and is increased in newborns with cystic fibrosis. 

In most cases, if a baby’s IRT is elevated, a second test will also be done on the newborn screening sample. This second test looks for changes in the gene that causes cystic fibrosis (called CFTR). Babies with high levels of IRT and at least one change in the CFTR gene may have cystic fibrosis.

Newborn screening for cystic fibrosis is important even if a mother already received screening during pregnancy. In some cases, newborn screening for cystic fibrosis may show different results than prenatal testing. It is important to always follow-up with an out-of-range newborn screening result– even if testing during pregnancy was normal. 
 

If your baby’s blood spot screening result for cystic fibrosis is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.

If your baby’s screening results show high IRT levels and only one change in the CFTR gene, this result does not mean that your baby definitely has cystic fibrosis. It does mean that your baby needs more follow-up testing.

If your baby’s screening results show high IRT levels and two or more changes in the CFTR gene, it is likely that your baby has cystic fibrosis and needs more follow-up testing.

To learn more about screening results, visit the Blood Spot Screening Results page.

Your baby may need the following tests after an out-of-range screening result:

• Sweat testing to check for the presence of increased chloride (salt)
• Blood and/or urine tests
• Genetic testing using a blood sample

You should complete any recommended follow-up testing as soon as possible. Babies with this condition can have serious health problems if they are not diagnosed and treated quickly.

False-positive newborn screening results for this condition can happen in the following cases:

• Babies who are cystic fibrosis carriers 
• Babies whose screening samples were collected before they were 24 hours old
• Babies who are very sick with conditions other than cystic fibrosis

False-negative newborn screening results for this condition can also happen. In some cases, babies with cystic fibrosis have normal levels of IRT and do not get picked up by screening.

Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need to get treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.

Signs of cystic fibrosis often appear shortly after birth, but some may not appear right away.

Signs may include the following:

• Salty sweat
• Thick mucus
• Frequent coughing or wheezing
• Diarrhea, greasy, or pale-colored stools
• Poor growth
• Weight loss
   

The condition is caused by a change in the CFTR gene. This gene gives your body instructions for making a channel made of protein that moves salt (chloride ions) in and out of cells. Salt controls the amount of water in and around cells. 

Without a working CFTR gene, this channel cannot keep a proper salt balance. An imbalance of salt means there is not enough water in mucus to keep it thin, so it becomes thick and sticky. The thick, sticky mucus blocks airways and ducts, causing problems with multiple systems in your baby’s body.

Cystic fibrosis is a genetic condition. Babies inherit it from their biological (birth) parents. To learn more about genetic conditions, visit MedlinePlus Genetics.

• Cystic fibrosis is an autosomal recessive condition. Babies inherit the condition when each parent passes down a nonworking CFTR gene to their baby. Only babies with two nonworking CFTR genes—one from the mom and one from the dad—have this condition.
  • People with one working copy and one nonworking copy of the CFTR gene are called carriers.
  • Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
  • If two parents are carriers of a nonworking copy of the CFTR gene, they have a 1 in 4 chance of having a child with cystic fibrosis.
  • Carriers for cystic fibrosis often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with cystic fibrosis.
  • Parents who already have a child with cystic fibrosis still have a 1 in 4 chance of having another child with cystic fibrosis. This 1 in 4 chance stays the same for all future children.
• Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it. Visit the National Society of Genetic Counselors to find a genetic counselor and the American College of Medical Genetics and Genomics to find a medical geneticist.