Pregnancy

Question

I would like to know whether CF can already be diagnosed when the mother is still pregnant.

Answer

To examine the unborn child for the presence of CF is usually done in a context when both partners are known to carry a CFTR mutation. (A person with CF carries 2 abnormal copies of the CFTR gene. A carrier has only one abnormal copy of the CFTR gene, the genetic material responsible for the disease CF. When both parents are carriers, they do not have the disease, but the risk that their child has CF will be 1 in 4.) This will most often occur in a family where there already is an older child having CF. Early in the pregnancy (around 11 weeks) a fibroblast test can be done. A small biopsy is taken from the placenta. On this material a DNA test is done. The material is checked for the presence of CFTR mutations, especially the CFTR mutations present in the parents. When the embryo carries 2 abnormal CFTR genes, the pregnancy can be terminated.

Of course most children are born in a situation where there is no concern about cystic fibrosis. In rare situations, during routine ultrasound, the intestines appear as ‘too intense’. This can be a manifestation of CF. That is an indication to check for the presence of CFTR mutations in both partners. When this is not the case, it is improbable (but not impossible) that the child is suffering from CF. (Routinely the 35 most frequent mutations are being evaluated. If neither partner carries one of these 35 mutations the chance of a CF child will be only 1 in 250.000 which is very low.) If the embryo is proven to have CF, termination
of the pregnancy can be considered. You should however know that ‘hyper-echogenic bowels’ are also seen in children who after birth appear to be totally healthy. The best solution will therefore be to do a sweat test after birth. The sweat test is still the reliable diagnostic test for CF.

Kind regards,

Dr. Mieke Boon
Prof K De Boeck

28.04.2011