Tests Before and During Pregnancy
Couples with a family history of CMT who are thinking of having a baby can be referred to a genetics specialist for advice.
A genetic counsellor can help couples work through the decision-making process and explain possible tests that can be carried out and any alternatives you may want to consider, such as adoption.
The main tests that can be carried out during pregnancy to check if a baby will develop certain types of CMT are:
- Chorionic villus sampling (CVS) – where a small sample of placenta is removed from the womb and tested for known CMT genes, usually between weeks 11 to 14 of pregnancy.
- Amniocentesis – where a sample of amniotic fluid is taken for testing, usually during weeks 15 to 20 of pregnancy.
If these tests show your child is likely to have CMT, you can discuss with your genetic counsellor whether you want to continue the pregnancy or have an abortion.
However, it's important to be aware that the results of these tests will not indicate how serious your child's CMT will be. This is because the symptoms and progression of the condition can vary widely, even among family members with the same type of CMT.
It's also important to bear in mind that both these tests can slightly increase your chances of having a miscarriage.
Pre-Implantation Genetic Diagnosis
For some couples at risk of having a child with CMT, pre-implantation genetic diagnosis (PGD) may be an option.
PGD involves using in-vitro fertilisation (IVF), where eggs are removed from a woman's ovaries before being fertilised with sperm in a laboratory. After a few days, the resulting embryos can be tested for certain types of CMT and a maximum of two unaffected embryos are transferred into the womb.
However, funding for PGD is decided on an individual basis. For example, you may be considered ineligible for PGD on the NHS if you already have unaffected children or if the chances of having a successful pregnancy are thought to be low. In these cases you can choose to fund PGD yourself, although each attempt is likely to cost at least £8,000.