Prenatal diagnosis and testing

What is prenatal diagnosis?

In the case of a pregnancy, if one or both parents are 'carriers' of a particular musclewasting condition (see the Muscular Dystrophy UK factsheet: Carrier testing and reproduction: your options), there is a risk that their unborn child will be affected by that condition.

'Prenatal tests' are carried out during pregnancy to try to find out if the foetus (unborn child) is affected. The tests are only available for some muscle-wasting conditions. You can check on availability by contacting your geneticist.

As a couple, you may want this information for two reasons: either to consider whether or not to continue the pregnancy if the foetus is affected, or to continue with the pregnancy armed with the information to prepare and plan for the future.

Different types of prenatal tests can be carried out at different times during the pregnancy:

1) non-invasive prenatal diagnosis (NIPD) – can be carried out from seven weeks’ gestation

2) chorion villus sampling (CVS) – at around 10-12 weeks

3) amniocentesis – at around 14-16 weeks

4) placental biopsy and foetal blood sampling – at around 18 weeks

5) ultrasound scanning to determine the gender of the baby (some conditions such as Duchenne muscular dystrophy will only affect boys in almost all cases) – at around 20 weeks.

Women/couples need to consider carefully which test to have and discuss this with their genetic counsellor, obstetrician or midwife. Earlier testing would allow early termination of the pregnancy, which would potentially be less traumatic for the couple, however it carries a slightly higher risk of miscarriage than later testing.

To get the maximum benefit from these tests, it is very important that investigations into carrier status should commence BEFORE a pregnancy is started. For this reason, many people choose to be carrier tested in their late teens.