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How do you get CF? How is CF diagnosed?

Cystic Fibrosis (CF) is a genetic condition, meaning that it is inherited from your parents, and cannot be caught later in life.1

1 in 19 of us are carriers of CF, meaning that we have one copy of a faulty gene that causes the condition but don’t have the condition itself.6 If a child with CF inherits a faulty copy of the gene from both parents, they will have CF.1


It is thought that prevalence of cystic fibrosis carries in the general population may be due to one copy of the faulty gene protecting against infections like Cholera and Tuberculosis2

The faulty genes adversely affect the movement of salt and water passing through cells in the body, which causes fluids in the body to become thick and sticky. This mostly causes problems in the lungs and digestive system where the thick, sticky fluid builds up: repeated lung infections and difficulty breathing because of blocked airways; and difficulty digesting and absorbing food leading to failure to thrive and inability to gain weight.3


Prospective parents may choose to have carrier testing before becoming pregnant to see how likely they are to have a child with CF. If both parents are carriers the likelihood is 1 in 4 (25%).1

Diagram of inheritance

There are also several tests that can be done during pregnancy to identify if the baby has CF such as chorionic villus sampling and amnicentesis.4

If CF is not diagnosed before birth, it is often diagnosed at birth or soon after with either a sweat test or a heel prick test, or because infant suffers from a common complication seen in new-borns with CF called meconiumileus where a portion of intestine is blocked.4,5,6,7

Approval code: RESP-IE-NP-00037

Date of preparation: November 2020

  1. What are the causes of cystic fibrosis? CF Trust. Available at: Last accessed: November 2020.
  2. Mowat A. Curr Pediatr Res. 2017; 21: 164 -171.
  3. What is cystic fibrosis? British Lung Foundation. Available at: Last accessed: November 2020.
  4. How is cystic fibrosis diagnosed? CF Trust. Available at: Last accessed: November 2020.
  5. Digestive system and cystic fibrosis. CF Trust. Available at: Last accessed: November 2020.
  6. CF Ireland Incidence of CF in Ireland. Available at:,work%20of%20Cystic%20Fibrosis%20Ireland. Last accessed: November 2020
  7. CF Ireland Newborn Screening. Available at: Last Accessed: November 2020

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