Prenatal Testing and Diagnosis of Cystic Fibrosis

Cystic fibrosis (CF) is an inherited disease that is caused by a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The CFTR protein is responsible for controlling the transportation of salt in and out of cells. Any mutations in the CFTR gene can cause an imbalance in the transport system, which can lead to the thick, sticky mucus that is known in CF patients. That mucus is what blocks the airways and causes bacteria to build up which can end up causing the CF patient to easily and frequently contract infections.

Carrier Testing

CF is the result of a person receiving a copy of the CFTR mutation from each of their parents. Parents (either both or one) can be carriers of CF without ever presenting with symptoms and can unknowingly pass the disease to their offspring.

Pregnant women often have the option to receive special testing to determine whether or not they are carriers of CF. The results of a pregnant woman's CF gene testing may help the mother and the physician decide whether or not the unborn baby should receive testing for CF. Cystic fibrosis carrier testing (or CFCT) generally covers only the most common CF mutations known in the U.S. The CFCT is not necessarily diagnostic for either the parents or the unborn baby, but may help to determine whether or not the baby is at risk of carrying the mutated gene.

The American College of Obstetricians and Gynecologists (ACOG) suggests that couples who have a family history of CF, have partners with CF, or are Caucasian of either European or Ashkenazi Jewish descent receive CFCT. The testing is done by a blood sample.

Some CF gene defects are rare and testing cannot detect them. While a negative test results means that the chance of being a CF carrier is small, it is still possible to be a carrier. If one of the partners shows to be a CF carrier, the other partner should be tested as well. If only one of the partners shows to be a CF carrier while the other partner tests negative, no further testing on the unborn baby is recommended. In the event that the father is not available for testing because he is either absent, deceased, or not willing, a genetic counselor can help the mother determine if prenatal testing is a viable option.

Prenatal Diagnosis

If both of the partners test positive for the CF gene, statistics say that there is a 25 percent chance that the baby will have CF. It is important to note that there is a greater chance that the baby will only be a carrier of CF and less likely chance that the baby will have CF. It is very possible that two parents who are both carriers of CF can have a baby that does not have CF.

In the event that both parents test positive as carriers of CF, prenatal testing will most likely convene to determine whether or not the baby has CF. Knowing that a baby has CF prior to birth can help the parents and doctors plan for the best course of action to care for the baby.

Depending on the physician and mother's decision, prenatal tests may include chorionic villus sampling (CVS) and amniocentesis. CVS is usually done after 9 full weeks of pregnancy and is carried out by taking a sample of tissue from the the placenta. Amniocentesis is generally done somewhere between 15 weeks and 20 weeks of pregnancy and is done by inserting a needle and withdrawing a trace amount of amniotic fluid for testing. These tests are not standard and are usually only recommended when there is cause for concern due the risk of miscarriage. The risk of miscarriage for both CVS and amniocentesis are about 1 in 300-500.

Pregnancy Complications with CF

While some women who have CF may have problems getting pregnant, many women can get pregnant and have a healthy baby. Many men who are carriers of CF may be infertile and unable to get their partner pregnant. Couples are encouraged to speak openly to their physician, obstetrician, or genetic counselor with any concerns about getting pregnant with CF factors.

While many women with CF can have a perfectly healthy pregnancies, some may have a higher risk for gestational diabetes. The increase in sugar that comes from diabetes can cause damage to organs in the body, including kidneys, eyes, nerves, and blood vessels. If a pregnant women has both CF and diabetes, extra care will have to be heeded in order to insure the safety of both mother and baby, both during and after pregnancy.

Managing Pregnancy with Cystic Fibrosis

If you are already pregnant along with having CF, there are a number of tips that you can follow to help ensure that your pregnancy is as healthy as possible:

1. Tell Your CF Care Team: You will want to tell your physician, dietician, physical therapist and anyone else who is on your CF care team right away if you are pregnant. They will be your best friend in insuring that you are doing everything you should (and avoiding everything you shouldn’t) be doing to make sure that both you and your baby are healthy.
2. Maintain (or Improve) Nutrition: When you have CF, it is already difficult to maintain your nutrition levels. Throw in a pregnancy and things can get pretty rough. Meet regularly with your CF care team and obstetrician to make sure you are getting all of the nutrients that you need. They may suggest that you take additional vitamin or mineral supplements to help you maintain adequate nutrition.
3. Decide if You Are Going to Breastfeed: Many women with CF fear that they will not be able to produce enough milk or nutritious enough milk to breastfeed their baby. If you think you would like to try breastfeeding your baby, talk with your nutritionist or obstetrician about getting the right amounts of protein and sodium added to your diet.
4. Continue CF Medications: Talk to your doctor and obstetrician about any medications you are currently taking or that you have taken recently. While the majority of inhaled and oral CF medications are generally safe during pregnancy, you will want to discuss them in detail with a specialist. You CF and pregnancy care team will help you make the best decisions.
5. Continue Chest Physiotherapy (CPT): Chest physiotherapy is an essential part of most CF patients' daily treatment plan. Most physicians will recommend that you continue your therapy to maintain your lung health and prevent infection during your pregnancy.
6. Fight Respiratory Infections Aggressively: If you have CF then you already know how important it is to aggressively fight off respiratory infections with antibiotics. During a pregnancy, fighting infections is even more crucial. Report any symptoms of infection to your CF care team immediately.

References

Alma, L. (2017). 7 Tips for Managing Your Pregnancy With Cystic Fibrosis. [Web]. In Very Well. Retrieved from: https://www.verywell.com/how-to-manage-pregnancy-with-cystic-fibrosis-998296

Brice, P. (2006). Genetic Screening for Cystic Fibrosis: An Overview of the Science and the Economics. [Web]. In Journal of Cystic Fibrosis. Retrieved from: http://www.sciencedirect.com/science/article/pii/S1569199307000124

Cystic Fibrosis: Prenatal Screening and Diagnosis. (2016). [PDF File][Web]. In The American College of Obstetricians and Gynecologists. Retrieved from: https://www.acog.org/Patients/FAQs/Cystic-Fibrosis-Prenatal-Screening-and-Diagnosis

Cystic fibrosis and pregnancy (2013). March of Dimes. [Web]. Retrieved from: http://www.marchofdimes.org/complications/cystic-fibrosis-and-pregnancy.aspx

Gonzalez, M. (2002). Prenatal Detection of a Cystic Fibrosis Mutation in Fetal DNA From Maternal Plasma. [Web]. In Prenatal Diagnosis. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/12378583

Hill, M. (2015). Non-invasive Prenatal Diagnosis for Cystic Fibrosis: Detection of Paternal Mutations, Exploration of Patient Preferences and Cost Analysis. [Web]. In Prenatal Diagnosis. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672687/

Shaffer, C. (n.d.). Tests for Cystic Fibrosis During Pregnancy. [Web]. In News Medical Life Sciences. Retrieved on 08/25/2017 from: https://www.news-medical.net/health/Tests-for-Cystic-Fibrosis-During-Pregnancy.aspx

Sparbel, K. (2009). Pregnancy as Foreground in Cystic Fibrosis Carrier Testing Decisions in Primary Care. [Web]. In Genetic Testing and Molecular Biomarkers. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2981356/