CF - prenatal diagnostics

Question

Is it possible to diagnose CF in an embryo or by prenatal examinations?

Answer

Dear questioner,
The question you’re asking is quite important for parents who already have a child with cystic fibrosis or for a couple where both partners are identified as carriers of a cystic fibrosis mutation. Both prenatal genetic testing and pre implantation diagnosis are available to these persons. The available techniques are most reliable if the specific mutations that caused CF in a previous child in that family are known. If not, less reliable techniques such as linkage analysis (evaluating a genetic marker in the vicinity of the CFTR gene that is most of the time inherited together with the CFTR gene) have to be used.
Pre-implantation genetic testing: genetic diagnosis outside of the womb before pregnancy is possible. Egg cells are collected from the ovary of the mother. Conception takes place ‘in vitro’ (in a test tube) with the semen of the father. Therefore this technique is called ‘IVF’ or in vitro fertilization. When the embryo is 3 days old, it will be examined in the laboratory to determine if it has CF. Only embryos without CF will be implanted in the womb of the mother. Per treatment the chance of succesful pregnancy is about 20%. This technique is possible in 1 centre in the Netherlands (Maastricht) and in one centre in Belgium (Brussels).
However, the legal status of pre-implantation genetic testing is very different in different European countries; in some, it is available, in others, such as in Germany, for example it is illegal.
Prenatal genetic testing:
Following a spontaneous pregnancy, a small tissue sample of the placenta is take in the 11th-13th week of pregnancy. These cells are then examined for the presence of CFTR mutations to determined if the future child will have CF or not. The results are available about 2 weeks later. If that result shows that the child does have CF, the pregnancy can be terminated on request of the parents.
If a family wishes to have children all these procedures and consequences should be discussed with them prior to going through these examinations. This can be discussed with a clinical geneticist or a specialized gynaecologist.
Dr. Christine de Die-Smulders

23.04.2009