Frequently Asked Questions

What is prenatal diagnosis?

Prenatal diagnosis is the identification of a structural abnormality or genetic disorder in a baby before birth. An example of a structural abnormality is a hole in the heart or spina bifida. Examples of genetic disorders are cystic fibrosis and Down’s syndrome.

Doctors use both invasive and non-invasive methods to make a diagnosis.

A non-invasive method carries no risk to mother or baby. For example, ultrasound scanning can be used to examine the anatomy of the baby, most commonly at around 20 weeks. Using ultrasound scanning, it is possible to diagnose abnormalities in the baby such as heart or kidney problems.

Chorionic villus sampling (CVS) and amniocentesis are procedures which enable doctors to diagnose genetic and chromosomal problems with the baby. As they involve inserting a fine needle into the womb, they are invasive procedures and they carry a risk of causing a miscarriage.

Why is prenatal diagnosis important?

Prenatal diagnosis is used:

1. To reassure couples that their baby is unlikely to have a problem. This includes couples with no family history, and couples with a ‘high risk’ pregnancy where there have been problems in the family.
2. To prepare parents for the birth of a baby with a structural or genetic problem
3. To enable babies who will require specialist care at birth or soon afterwards to be born in a hospital where the right care is available.
4. To give parents a choice to end a pregnancy where the baby has a serious abnormality and is unlikely to survive or will be born with a significant disability

When might an invasive procedure be offered?

Invasive procedures are offered to parents whose babies are known to have an increased risk of having a chromosomal or genetic disorder.

What are invasive tests?

These include chorionic villus sampling (CVS), amniocentesis and less frequently fetal blood sampling. Invasive tests always involve inserting a needle into the womb to obtain genetic material from the baby or placenta and as a result of this carry small risk of miscarriage.

What is a non-invasive test?

Ultrasound scanning and simple blood tests taken from the woman are examples of non-invasive tests. These methods are commonly used in prenatal diagnosis and present no risk to the pregnancy.

What is a CVS?

A CVS is also known as a placental biopsy and can be carried out between 11 & 13 weeks of pregnancy. A small piece of placenta (afterbirth) is obtained and sent to a laboratory for specialised testing. The sample can be taken via a fine needle through the abdomen (trans-abdominally) or using a special pair of forceps through the cervix (trans-cervically). Your doctor will usually advise on the best method for you as it depends on where the placenta has attached to womb. The procedure can be uncomfortable but does not usually last for more than a couple of minutes. Because a sample is taken from the pregnancy it carries around a 1% risk of miscarriage.

What is an amniocentesis?

An amniocentesis can be carried out from 15 weeks of pregnancy and involves taking a sample of the fluid from around the baby which will be sent to a laboratory for testing. A fine needle is passed through the woman’s abdomen and into the womb; a small sample of the fluid is then taken. This procedure can also be uncomfortable but again is usually over within a couple of minutes. Amniocentesis carries a 1% risk of miscarriage.

How is SAFE reducing the risks of prenatal diagnosis?

SAFE has a team of professionals from all over the world working on Non-Invasive Prenatal Diagnosis (NIPD). NIPD is a new method which allows doctors to test unborn babies for specific conditions by using a sample of the mother’s blood alone. Therefore reducing the number of healthy babies lost as a direct result of invasive procedures.

How does non-invasive prenatal diagnosis (NIPD) work?

NIPD utilises cell free fetal DNA (ffDNA). DNA is the genetic material that is in all the cells in our body. The pattern of DNA makes up the genes that code for our characteristics, such as hair and eye colour, and any genetic conditions we may have or carry. ffDNA is genetic material which comes from the baby but can be detected in the mother’s blood during pregnancy. The exact mechanism as to how the baby’s DNA – the ffDNA - finds its way into the mother’s bloodstream is not clear. However scientists have discovered that ffDNA is present from 6 weeks of pregnancy and is undetectable 2 hours after the baby is born. This means that theoretically a woman could have a simple blood test without any risk to the baby from 6 weeks of pregnancy and get a result before a CVS or amniocentesis can even be performed.

Can NIPD using ffDNA be used now?

It can only be used in a few circumstances. This is because there is a lot more of the mother’s free DNA in the mother’s blood than there is of the baby’s, so the mother’s DNA swamps the baby’s. At the moment we cannot separate the two types of DNA completely and so it is difficult to look for small changes in the two types of DNA that might mean that the baby has a problem not found in the mother.

When is NIPD currently being used in prenatal diagnosis?

NIPD is presently offered to women whose babies are at risk of Haemolytic Disease of the Newborn (HDN) or a genetic disease in which only affects a particular sex e.g. Duchenne Muscular Dystrophy.

See our patient information leaflet which explains how the test works and explores how SAFE is making a real difference to parents by dramatically reducing rates of invasive testing.

How will NIPD be used in the future?

Scientists are striving to develop new methods that will detect common chromosomal and genetic conditions such as Down’s syndrome and cystic fibrosis. However, many improvements are required before the techniques can be applied to most genetic conditions. This is why SAFE is coordinating a collaboration of work from scientists all over the world.

Is NIPD available for me?

NIPD is currently only available for the medical reasons mentioned above and has to be requested by a health professional. If your baby is at risk of one of these conditions you should speak to a member of the medical team caring for you. Alternatively, if you have any doubts as to whether these tests might be useful for you could discuss it with your family doctor or GP who can refer you to a geneticist or obstetrician if necessary.