Genetic tests during pregnancy

During pregnancy, genetic tests can show if a baby has the changed gene for a condition. But it cannot always tell you what symptoms your child will have after they’re born, or when symptoms may appear.

If you’re worried about your baby inheriting a muscle wasting condition, speak to your GP, midwife, or neuromuscular team. They can refer you to a genetic counsellor. This is a professional who can support you to make decisions about genetic testing. They can help you understand how genetic tests can help and what the results may mean for you and your family.

Muscle wasting conditions are passed through families in different ways. You can read more about this on our page about how muscle wasting conditions are inherited.

Some people carry a changed gene for a muscle wasting condition. This means they do not have the condition themselves, but they can pass the changed gene to their children. If a child inherits this gene, they may be unaffected (a carrier) or they may have the condition. The chance of this happening depends on how the condition is inherited. If you have a family history of a muscle wasting condition, you might want to think about carrier testing. We have more information about this on our page about carrier testing when you’re planning a pregnancy.

Prenatal testing involves testing an unborn baby’s DNA to see if they have inherited a particular genetic condition. You may be able to have testing as part of fertility treatment (pre-implantation genetic testing) or during pregnancy.

Prenatal testing can diagnose many muscle wasting conditions, but not all. A genetic counsellor can help you understand how testing can help you and your family. You do not have to have prenatal testing – it’s your choice.

PGT aims to create a pregnancy that is not affected by a particular genetic condition. It used to be called pre-implantation genetic diagnosis (PGD).

PGT can help families affected by some muscle wasting conditions. It uses fertility treatment to create embryos from the parents’ eggs and sperm. This is done in a laboratory. A few cells from each embryo are tested for the gene that causes the condition. An embryo that does not have the affected gene can then be placed into the womb. This means the embryo has the chance to develop into a baby that does not have the muscle wasting condition.

You can use your embryos straight away or freeze them to use in the future.

You may choose to have PGT if you meet all the conditions for treatment. For example:

• You have, or have a family history of, a condition caused by a single, known gene.
• Your children are likely to inherit the condition, and you and your partner do not have an unaffected child together.
• The condition has been approved for PGT – there is a list of approved conditions. If not, the genetic clinic can ask for it to be approved. This can take a long time and may not be successful.
• You meet the criteria for fertility treatment. Your GP can tell you about this or you can read Genetic Alliance UK’s information about pre-implantation genetic testing.

PGT can take a long time. It may take about 8 to 18 months before you start treatment. It can take longer if the condition has not already been approved for testing.

The chance of having a successful pregnancy depends on a few things. For example, your age and whether you have any fertility problems. About one in three people will have a successful pregnancy after fertility treatment with PGT.

A genetic counsellor can explain the benefits and risks of PGT, to help you decide whether it’s right for you and your family.

Non-invasive prenatal diagnosis (NIPD)

NIPD uses a blood sample from the mother to diagnose a genetic condition in the unborn baby. The mother’s blood contains a mix of their DNA and DNA from the placenta. The placenta is an organ that passes food and oxygen to the baby during pregnancy. DNA from the placenta is very similar to the baby’s DNA.

NIPD can diagnose some single-gene muscle wasting conditions in unborn babies. It can also show the sex of the baby, which is important for conditions that mainly affect either males or females.

If you can, speak to your GP or neuromuscular team about NIPD before getting pregnant. Tests for some conditions need to be prepared before pregnancy.

If you’re able to have NIPD, you’ll have an early scan to confirm your dates, and a blood test from eight or nine weeks of pregnancy.

NIPD does not harm the baby at all. But it’s not suitable for everyone. For example, you may not be able to have it if you’re pregnant with more than one baby.

Chorionic villus sampling (CVS)

CVS involves taking a tiny sample of the placenta for genetic testing. This can show whether the baby has inherited a particular muscle wasting condition.

You can have CVS between 11 and 14 weeks of pregnancy. A healthcare professional uses an ultrasound scan to guide a thin needle through your tummy area (abdomen). You’ll be awake during the test, but you’ll have a local anaesthetic to numb the area. Many people describe the procedure as uncomfortable, but it should not be painful. You may have some period-like cramps afterwards. Try to avoid energetic or heavy physical activity for a couple of days.

Sometimes the test cannot be completed if it’s difficult to reach the placenta. You may be offered another CVS in a week or two, or you may choose to wait and have an amniocentesis.

There’s a small chance of miscarriage after CVS. On average, about 1 in 200 people may miscarry after having the test. Your genetic counsellor, midwife, or doctor can tell you more about the chance of miscarrying.

You can have CVS if you are pregnant with more than one baby. You will need to have the test in a specialist unit due to the higher chance of complications. About 1 in 100 people expecting more than one baby may miscarry after having CVS.

If you’re thinking of having CVS, your healthcare team will help you understand the benefits and risks of the test.

Amniocentesis

Amniocentesis involves taking a sample of fluid that surrounds the baby in the womb. This is called amniotic fluid, and it contains genetic material (DNA) from the baby. This DNA can be used for genetic testing.

You can have amniocentesis from 15 weeks of pregnancy. A healthcare professional uses an ultrasound scan to guide a thin needle through your tummy area (abdomen). They remove about 20ml (four teaspoons) of amniotic fluid.

Many people describe the procedure as uncomfortable, but it should not be painful. You may have some period-like cramps afterwards. Try to avoid energetic or heavy physical activity for a couple of days.

There’s a small chance of miscarriage after amniocentesis. On average, about 1 in 200 people may miscarry after having the test. Your genetic counsellor, midwife, or doctor can tell you more about the chance of miscarrying.

You can have amniocentesis if you are pregnant with more than one baby. You will need to have the test in a specialist unit due to the higher chance of complications. About 1 in 100 people expecting more than one baby may miscarry after having amniocentesis.

If you’re thinking of having amniocentesis, your healthcare team will help you understand the benefits and risks of the test.

Pre-implantation genetic testing and prenatal tests can give you information to help you plan a pregnancy. They can lead to some difficult decisions about whether to start or continue a pregnancy. But there is support available to help you decide what’s best for your family. Your genetic counsellor can answer your questions and talk to you about your options.

Support groups and organisations can give you support and information. The charity Antenatal Results & Choices has information about genetic tests and a parent’s forum. You can also contact our helpline team for information and advice.