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  • Elizabeth Kearney, MS, CGC

What people planning for pregnancy should know about carrier testing for cystic fibrosis

Updated: May 20

Most prenatal and fertility providers will offer cystic fibrosis carrier testing to their patients, but by the time a woman is pregnant, many options are no longer available to her and her partner.


Who should know about carrier testing for cystic fibrosis?


The American College of Obstetricians and Gynecologists (ACOG) recommends cystic fibrosis (CF) carrier testing for all pregnant women or women considering pregnancy. CF carrier testing is not required. It is a very personal decision, but sometimes the decision can feel rushed if a woman doesn’t hear about carrier testing until her first prenatal appointment. There are also more options available to couples who have a higher chance to have a child with CF if they know about those chances prior to pregnancy. Therefore, it is important for people who are pregnant or planning for pregnancy to learn about CF carrier testing as early as possible.


What is cystic fibrosis?


Cystic fibrosis (CF) is one of the more common inherited conditions, affecting about 30,000-35,000 people in the United States across all races and ethnicities. About 1,000 people are diagnosed with CF each year.

People with CF have a thick, sticky mucus that makes it difficult to clear their lungs easily the way other people do. As a result, germs, like bacteria, can get trapped in their lungs, causing lung infections (respiratory illnesses) more often. The illnesses last longer and cause damage to lung tissue over time. Eventually, lung damage can get so severe that a person’s lungs fail and they may need a lung transplant to survive. To postpone lung damage as long as possible, most people with CF undergo daily treatment to open their airway and shake the mucus loose to cough it up.

Some people with CF also have issues with the pancreas, an organ that is important in secreting certain chemicals called enzymes that help with digestion. The sticky mucus can clog the pancreas from releasing enzymes like it should. If they are not diagnosed right away, children with CF may have difficulty gaining weight and have messy, smelly bowel movements. People with a diagnosis of CF can take supplements that replace the natural enzymes that they don’t make themselves, and this will help them maintain a healthy weight.


Cystic fibrosis is not the same in everyone.

Each person with CF will experience a different pace of the disease and may not have all the symptoms. Also, treatment for CF has improved in recent years, so it is important to learn from experts what to expect when a diagnosis is made.


What causes cystic fibrosis?


Cystic fibrosis is an inherited disorder.

A person with CF has two non-working copies of a particular gene.

Genes are the blueprint that tell the body how to grow, develop, and function. Sometimes there is a difference in a gene, called a variant, that causes the gene not to work properly. The gene that causes CF codes for a substance, called a chloride channel, that sits on the lining of cells and regulates a chemical called chloride in and out of the cell. The chloride channel doesn’t work right in people with CF and is why people with CF sometimes notice a salty substance on their skin.


How is cystic fibrosis inherited?


People have two copies of most genes. One gene is from the mother and one from the father. A person with cystic fibrosis has a non-working copy of the gene from the mother and one from the father. The parents are called carriers because they each have a working copy of the gene, which keeps them healthy, as well as a non-working copy of the gene. Carriers do not typically have severe health problems although some men who are carriers may have fertility issues.


If a couple planning for pregnancy are both carriers for CF, they have a 1 in 4 chance in each pregnancy to have a child with CF.

How would people planning for pregnancy know that they are carriers for cystic fibrosis?

Many people who are carriers of cystic fibrosis would have no way of knowing without specialized testing. People who are pregnant or considering pregnancy can have carrier testing for cystic fibrosis. Carrier testing involves giving a blood or saliva sample to a laboratory that specializes in genetic testing. The laboratory studies the person's DNA to determine if he or she is a carrier for CF.


Carrier testing for cystic fibrosis is often combined with carrier testing for other inherited disorders. You can read about carrier testing in our blog post Hidden Genes.


What are the possible results from cystic fibrosis carrier testing for people planning for pregnancy?

A positive result means that the person is a carrier. Most of the time, carriers do not have any symptoms of CF. However, if one partner is found to be a carrier of cystic fibrosis, it would be appropriate for the person’s partner to have CF carrier testing too. If the partner is a carrier, too, the couple has a 1 in 4 chance to have a child with CF.



If the results of CF carrier testing are negative, it is much less likely that the person is a CF carrier. However, the chances are not zero. Current science is not able to find all possible genetic changes that can cause cystic fibrosis.



Many laboratories only report variants in the CF gene that are known to cause disease. However, there can be changes in the CF gene that are not yet understood. As scientists’ understanding of genetics improves, it's possible that some of those unknown variants may be reclassified as positive or negative results.


If a couple knows that they are both carriers for cystic fibrosis, is there anything they can do?


Couples who know they are both carriers for cystic fibrosis have some options to consider.

  • In vitro fertilization (IVF) to perform genetic testing on embryos (called preimplantation genetic testing or PGT)

  • Egg or sperm donation

  • Testing a future pregnancy

  • Adoption

  • Using time to learn about cystic fibrosis

  • Deciding not to have children.

When should people planning for pregnancy consider carrier testing for cystic fibrosis?


The earlier people consider carrier testing, the more options they are likely to have. Most prenatal care and fertility providers will offer cystic fibrosis carrier testing to their patients. However, by the time a woman or couple is pregnant, it is too late to consider some of the options described above, like adoption, egg or sperm donation, or IVF to allow genetic testing on embryos, if they are both found to be carriers for cystic fibrosis.


Does insurance cover carrier testing for cystic fibrosis?


Many health insurance plans will cover carrier testing, particularly for pregnant women. However, as was just stated, waiting until pregnancy may mean that fewer options will be available to a couple who are found to be carriers of cystic fibrosis. Therefore, it is smart to check your healthplan to find out what your options are. Also, many labs offer carrier testing for a cash rate of about $250, or even less in some cases.


Do women have to have cystic fibrosis carrier testing?


The decision of whether to have carrier testing is a personal one. Many people decide to have carrier testing, but many decide against it. Only the woman or couple who are planning to start a family can know what is best for them.


What should a woman or couple do next if they decide they want carrier testing for cystic fibrosis?


The American College of Obstetricians and Gynecologists (ACOG) recommends cystic fibrosis (CF) carrier testing for all pregnant women or women considering pregnancy. CF carrier testing is not requuired. I very personal decision, but sometimes the decision can feel rushed if a woman doesn’t hear about carrier testing until her first prenatal appointment. There are also more options available to couples who have a higher chance to have a child with CF if they know about those chances prior to pregnancy. Therefore, it is important for people who are pregnant or planning for pregnancy to learn about CF carrier testing as early as possible. rrier testing until the first prenatal appointment. As explained above, fewer options will be available to women and couples at that time.





Sources:

  1. American College of Obstetricians and Gynecologists. Carrier Screening for Genetic Conditions. Committee Opinion No. 691 2017.

  2. Cystic Fibrosis Foundation. “About CF” Accessed May 18, 2021. https://www.cff.org/What-is-CF/About-Cystic-Fibrosis/

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