Genotype 5T/7T at the IVS8 polyT site of the CFTR gene

Question

I am currently 23 weeks pregnant. After two findings (echogenic bowel and echogenic focus in the left ventricle) during my second-trimester ultrasound, I proceeded with an NIPT test and a molecular test for Cystic Fibrosis (for 34 mutations, whereas before pregnancy, I had only been tested for the ΔF508 mutation).

The Cystic Fibrosis test results state:

"The tested sample is negative for the above CFTR gene mutations and carries the 5T/7T genotype at the IVS8 polyT site of the CFTR gene."

Additionally, the report includes the following note:

"It is noted that the presence of the 5T polymorphism (IVS8-5T) is associated with Congenital Bilateral Aplasia of the Vas Deferens (CBAVD) in males."

I should mention that my partner has not been tested for Cystic Fibrosis, and we are expecting a baby girl.

Could you explain how these results could affect a future pregnancy if the baby is a boy?

Thank you in advance!

Answer

Since there are ultrasound findings that may be related to cystic fibrosis (ultrasound bowel) it is recommended to do a full test for the CFTR gene. Testing only 34 mutations does not guarantee a high percentage.
The risk assessment can only be done comprehensively if both members of the couple have been tested.
Best regards,
M. Poulou

25.04.2025