Amniocentesis is only offered to pregnant women who have a higher chance of having a baby with a genetic or chromosomal condition. It can diagnose a range of conditions.

If your test results or medical or family history suggest you have a higher chance of having a baby with a genetic or chromosomal condition, you may be offered amniocentesis.

You do not have to take the test. It's up to you to decide whether you want it.

What conditions can amniocentesis detect?

Amniocentesis can be used to diagnose a number of conditions, including:

• Down's syndrome – all children born with Down's syndrome have some degree of learning disability and delayed development, but this varies widely between individual children
• Edwards' syndrome and Patau's syndrome – conditions that can result in miscarriage, stillbirth or severe physical problems and learning disabilities
• cystic fibrosis – a condition where the lungs and digestive system become clogged with thick, sticky mucus
• muscular dystrophy – a condition causing progressive muscle weakness and disability
• sickle cell disease – where the red blood cells develop abnormally and are unable to carry oxygen around the body properly
• thalassaemia – a condition that affects red blood cells and can cause anaemia, restricted growth and organ damage

Deciding whether to have amniocentesis

If you're offered amniocentesis, ask your doctor or midwife what the procedure involves, and about the risks and benefits, before deciding whether to have it.

You may also find it helpful to contact a support group, such as Antenatal Results and Choices (ARC), a charity that offers information, advice and support on all issues related to screening during pregnancy.

Reasons to have amniocentesis

The test will usually be able to tell you for certain if your baby will or will not be born with any of the conditions tested for.

You might find that your baby does not have the condition screening tests said they might have, which can be reassuring.

But if the test confirms that your baby does have the condition they were tested for, you can decide how you'd like to proceed.

Find out more about the results of amniocentesis

Reasons not to have amniocentesis

There's a risk of miscarrying the baby. Up to 1 out of every 100 women who have amniocentesis will miscarry. You may feel this outweighs the potential benefits of the test.

Some women decide they'd rather find out if their baby has a genetic condition when their baby's born.

Find out more about the risks of amniocentesis

Amniocentesis involves taking a small sample of amniotic fluid so the cells it contains can be tested. Amniotic fluid surrounds the unborn baby (foetus) in the womb (uterus).

Preparing for amniocentesis

You will not usually need to do anything special to prepare for amniocentesis. You can eat and drink as normal beforehand.

In some cases, you may be advised to avoid going to the toilet for a few hours before the test because it's sometimes easier when your bladder is full.

Your doctor or midwife will tell you about this before you attend your appointment.

You can bring a partner, friend or family member for support when you have the test.

Ultrasound scan

You'll have an ultrasound scan before and during amniocentesis.

An ultrasound scan uses high-frequency sound waves to produce an image of your womb that's relayed to a monitor.

The ultrasound scan allows healthcare professionals to:

• check the position of the baby
• find the best place to remove some amniotic fluid
• ensure the needle can pass safely through the walls of your tummy (abdomen) and womb

Anaesthetic

Before the needle is inserted into your abdomen, the area may be numbed with anaesthetic.

This involves having a small injection into your belly and may sting slightly.

But anaesthetic is not usually necessary because research suggests it does not have much effect in most cases.

How amniocentesis is performed

An antiseptic solution will first be used to clean your tummy (abdomen) to minimise the risk of infection.

A long, thin needle is then inserted through your abdominal wall. It may cause a sharp stinging sensation.

Using the ultrasound image as a guide, the needle is passed into the amniotic sac that surrounds the baby.

A syringe is then used to remove a small sample of the amniotic fluid, which will be sent to a laboratory for analysis.

In around 6 in every 100 women having amniocentesis, there's a problem drawing out enough fluid, so the needle has to be reinserted a second time. This is usually because of where the baby is positioned.

If the second attempt is also unsuccessful, you'll be offered another appointment.

Is amniocentesis painful?

Amniocentesis is not usually painful, but you may feel uncomfortable during the procedure.

Some women describe experiencing a pain similar to period pain or feeling pressure when the needle is taken out.

How long does it take?

The procedure usually takes around 10 minutes, although the whole consultation may take about 30 minutes.

Afterwards, you'll be monitored for up to an hour in case the test causes any side effects, such as heavy bleeding.

You can then go home to rest. It's a good idea to arrange for someone to drive you home, as you might not feel up to it yourself.

Recovering after amniocentesis

After amniocentesis, it's normal to have cramps similar to period pain and light vaginal bleeding called spotting for a few hours.

You can take over-the-counter painkillers such as paracetamol (but not ibuprofen or aspirin) if you experience any discomfort.

You may wish to avoid any strenuous activity for the rest of the day.

Contact your midwife or the hospital where the procedure was carried out for advice as soon as possible if you develop any of the following symptoms after the procedure:

• persistent or severe pain
• a high temperature
• chills or shivering
• discharge or clear fluid from the vagina
• contractions (when your abdomen tightens then relaxes)
• vaginal bleeding

After amniocentesis has been carried out, the sample of amniotic fluid will be sent to a laboratory for testing.

Getting the results

The first results should be available within 3 working days, and this will tell you whether a chromosomal condition, such as Down's syndrome, Edwards' syndrome or Patau's syndrome, has been found.

If rarer conditions are also being tested for, it can take 3 weeks or more for the results to come back.

You can usually choose whether to get the results over the phone, or during a face-to-face meeting at the hospital or at home.

You'll also receive written confirmation of the results.

What the results mean

Amniocentesis is estimated to give a definitive result in 98 to 99 out of every 100 women having the test.

But it cannot test for every condition and, in a small number of cases, it's not possible to get a conclusive result.

Many women who have amniocentesis will have a "normal" result. This means that none of the conditions that were tested for were found in the baby.

But a normal result does not guarantee that your baby will be completely healthy, as the test only checks for conditions caused by certain genes and it cannot exclude every condition.

If your test result is positive, your baby has 1 of the conditions they were tested for.

In this instance, the implications will be fully discussed with you and you'll need to decide what to do next.

What happens if a condition is found

If the test finds that your baby will be born with a condition, you can speak to a number of specialists about what this means.

These could include a midwife, a doctor who specialises in childrens' health (consultant paediatrician), a geneticist and a genetic counsellor.

They'll be able to give you detailed information about the condition to help you decide what to do, including the possible symptoms your child may have, the treatment and support they might need, and whether their life expectancy will be affected.

A baby born with 1 of these conditions will always have the condition, so you'll need to consider your options carefully.

Your options are to:

• continue with your pregnancy – it can help to find out as much as you can about the condition your baby will have
• end your pregnancy (have a termination)

This can be a very difficult decision, but you do not have to make it on your own.

As well as discussing it with specialist healthcare professionals, it can help to talk things over with your partner and speak to close friends and family.

You can also get support and more information from charities like:

• Antenatal Results and Choices (ARC)
• Down's Syndrome Association
• Sickle Cell Society
• SOFT (Support Organisation for Trisomy 13 and 18)

Before you decide to have amniocentesis, you'll be told about the risks and possible complications.

The main risks associated with the procedure are outlined below.

Miscarriage

There's a small risk of loss of the pregnancy (miscarriage) occurring in any pregnancy, regardless of whether or not you have amniocentesis.

If you have amniocentesis after 15 weeks of pregnancy, the chance of having a miscarriage is estimated to be up to 1 in a 100.

The risk is higher if the procedure is carried out before 15 weeks.

It's not known for certain why amniocentesis can lead to a miscarriage. But it may be caused by factors such as infection, bleeding or damage to the amniotic sac that surrounds the baby.

Most miscarriages that happen after amniocentesis occur within 3 days of the procedure. But in some cases it can occur up to 2 weeks later.

There's no evidence that you can do anything during this time to reduce your risk.

Infection

As with all surgical procedures, there's a risk of infection during or after amniocentesis.

But the rate of severe infection for amniocentesis is lower than 1 in 1,000.

Rhesus disease

If your blood type is rhesus (RhD) negative but your baby's blood type is RhD positive, it's possible for sensitisation to occur during amniocentesis.

This is where some of your baby's blood enters your bloodstream and your body starts to produce antibodies to attack it.

If it's not treated, this can cause the baby to develop rhesus disease.

If you do not already know your blood type, a blood test will be carried out before amniocentesis to see if there's a risk of sensitisation.

An injection of a medication called anti-D immunoglobulin can be given to stop sensitisation occurring.

Find out more about preventing rhesus disease

Club foot

Having amniocentesis early (before week 15 of the pregnancy) has been associated with an increased risk of the unborn baby developing club foot.

Club foot, also known as talipes, is a congenital (present at birth) deformity of the ankle and foot.

Because of the increased risk of a baby developing club foot, amniocentesis is not recommended before 15 weeks of pregnancy.