Screening for sickle cell and thalassaemia

Sickle cell disease (SCD) and thalassaemia are inherited blood disorders. If you are a carrier of sickle cell or thalassaemia, you can pass these conditions on to your baby.

All pregnant women in England are offered a blood test to find out if they carry a gene for thalassaemia, and those at high risk of being a sickle cell carrier are also offered a test for sickle cell. If the mother is found to be a carrier, screening is also offered to the father.

This test should be offered before you're 10 weeks pregnant. It's important the test is done early – if you find out you're a carrier, you and your partner will have the option of further tests to know if your baby will be affected.

This page covers:

Why will I be offered screening in pregnancy?
What does the screening test involve?
Do I have to have this screening test?

Getting your screening results
Further tests in pregnancy if the mother's a carrier
If your unborn baby has sickle cell disease or thalassaemia major

What if I decide not to have screening when I'm pregnant?
Can anyone have a test for sickle cell and thalassaemia?
Finding out you're a carrier
What if I get pregnant and already know I'm a carrier or my partner is a carrier?

About sickle cell and thalassaemia

Sickle cell disease and thalassaemia major affect haemoglobin, a part of the blood that carries oxygen around the body. People who have these conditions will need specialist care throughout their lives.

People with sickle cell:

• can have episodes of very severe pain
• can get serious, life-threatening infections
• are usually anaemic – their bodies have difficulty carrying oxygen

Babies with sickle cell disease can receive early treatment, including immunisations and antibiotics.

This, along with support from their parents, will help prevent serious illness and allow the child to live a healthier life.

Find out more about sickle cell disease.

People with thalassaemia major are very anaemic and need a blood transfusion every three to five weeks, as well as injections and medicines throughout their lives.

Read more about thalassaemia.

There are also other less common, and less serious, haemoglobin disorders that may be found through screening.

Why will I be offered screening for sickle cell and thalassaemia early in pregnancy?

Screening is offered to find out if you are a carrier of a gene for sickle cell or thalassaemia and therefore likely to pass it on to your baby.

Genes are the codes in our bodies for things like eye colour and blood group. Genes work in pairs: for everything we inherit, we get one gene from our mother and one gene from our father.

People only have sickle cell disease or thalassaemia major if they inherit two unusual haemoglobin genes – one from their mother and one from their father.

People who inherit just one unusual gene are known as "carriers", or as having a "trait".

Carriers are healthy and do not have the disease. Sickle cell carriers can experience some problems in situations where their bodies might not get enough oxygen, such as having a general anaesthetic.

All carriers can pass the unusual gene on to their children.

When both parents are carriers

When both parents are carriers, each time they are expecting a child there is:

• a one in four (25%) chance of the child not being affected – the baby will not have or carry the disease
• a one in four (25%) chance of inheriting both unusual haemoglobin genes and having the disease
• a two in four (50%) chance of inheriting one unusual haemoglobin gene and being a carrier

Anyone can be a carrier of haemoglobin disease. However, it is more common among people with ancestors from Africa, the Caribbean, the Mediterranean, India, Pakistan, south and southeast Asia, and the Middle East.

Read more about being a carrier of sickle cell disease or a carrier of thalassaemia.

What does the screening test involve?

Screening for sickle cell and thalassaemia involves a blood test. It's best to have the test before you are 10 weeks pregnant.

This is because you'll have the option of more tests to find out whether your baby will be affected if this first test shows you're a carrier of a blood disorder.

By having the test early, you and your partner can find out about all your options and make an informed decision if your baby is at risk of inheriting a blood disorder – see Further tests if the mother is a carrier.

All pregnant women are offered a test for thalassaemia, but not all women are automatically offered a test for sickle cell.

In areas where haemoglobin diseases are more common, all women will automatically be offered a blood test for sickle cell.

In areas where haemoglobin diseases are less common, a questionnaire is used to identify your family origins and the origins of the baby's father.

If the questionnaire shows that either you or the baby's father is at risk of being a sickle cell carrier, you will be offered a screening test.

You can ask to have the test even if your family origins do not suggest the baby would be at high risk of a haemoglobin disease.

Can this screening harm me or my baby?

No, the screening test cannot harm you or your baby, but it is important to think carefully about whether or not to have this test.

It can provide information that may mean you have to make further important decisions. For example, you may be offered further tests that have a risk of miscarriage.

Do I have to have this screening test?

No, you do not have to have the screening test. Some people want to find out if their baby has sickle cell disease or thalassaemia, while others do not.

Getting your screening results

The test will tell you if you are a carrier or not, or whether you have the disease yourself.

You will get the result of the blood test within two weeks. The person doing the test will discuss the arrangements for getting your results to you.

If you are found to be a carrier of sickle cell or thalassaemia, you will be contacted by a specialist nurse or midwife counsellor for genetic counselling.

Further tests in pregnancy if the mother is a carrier

Testing to see if the father is a carrier

If the screening test finds that you are a carrier of a haemoglobin disease, your baby's father will also be offered a blood test.

If tests show the father is not a carrier, your baby will not have sickle cell disease or thalassaemia major and you will not be offered further tests in pregnancy.

However, there is still a 50% chance your baby could be a carrier and pass on the unusual gene to their children.

You can discuss the implications of you or your baby being a carrier with your GP or a healthcare professional at your local sickle cell and thalassaemia centre.

Read more about finding out you're a carrier.

Diagnostic tests when both parents are carriers

If tests show your baby's father is also a carrier, there is a one in four chance (25%) that your baby can have the disease.

You will be offered further tests called diagnostic tests to find out if your baby is affected. A diagnostic test will tell you:

• if your baby has sickle cell disease, thalassaemia major or another haemoglobin disorder
• if your baby is a carrier
• if your baby is completely unaffected

If the baby's father is not available and you have been identified as a carrier, you will be offered a diagnostic test.

About 1 in 100 diagnostic tests result in a miscarriage. It is up to you whether or not to have the diagnostic test.

It can be a very difficult time if you are told you are at risk of having a baby with sickle cell disease or thalassaemia major. You can talk to your midwife, specialist nurse or doctor about your situation and your options.

You can also get information and support from the charity Antenatal Results and Choices (ARC). They have a helpline you can call for information and support on 0845 077 2290, or 020 7713 7486 from a mobile.

There are two types of diagnostic test:

• chorionic villus sampling (CVS) – this is usually performed from 11 to 14 weeks of pregnancy. A fine needle, usually put through the mother's abdomen, is used to take a tiny sample of tissue from the placenta. The cells from the tissue can be tested for sickle cell or thalassaemia. Read more about CVS.
• amniocentesis – this is done from 15 weeks of pregnancy. A fine needle is passed through the mother's abdomen into the uterus to collect a small sample of the fluid surrounding the baby. The fluid contains some of the baby's cells, which can be tested for sickle cell or thalassaemia. Read more about amniocentesis.

If you find out your unborn baby has sickle cell disease or thalassaemia major

If the result shows your baby has sickle cell disease or thalassaemia major, you will be offered an appointment with a health professional. You will be able to get information about the condition the baby has inherited and talk through your choices.

Some conditions are more serious than others. Some women decide to continue with the pregnancy, while others decide they do not want to continue with the pregnancy and have a termination (abortion).

If you are faced with this choice, you will get professional support to help you make a decision. Support for parents is also available from the charity ARC.

If the test shows you are a carrier, there is a chance that other members of your family could be carriers, too. You may want to encourage them to ask for a test, especially if they are planning to have a baby.

Find out more about what to expect when a screening test suggests there might be a problem.

What if I decide not to have screening when I'm pregnant?

If you choose not to have the screening test, your baby can still have screening for sickle cell disease as part of newborn blood spot screening a few days after the birth.

Can anyone have a test for sickle cell and thalassaemia at any time?

Although testing for sickle cell and thalassaemia is only offered during pregnancy, anyone can ask their GP or local sickle cell and thalassaemia centre for a free test at any time.

If you or your partner are concerned you may be a carrier, perhaps because someone in your family has a blood disorder or is a carrier, it's a good idea to get tested before you start a family.

That way you can understand your risk of passing on a blood disorder to any children you have, and discuss options for a healthy pregnancy with your GP or another healthcare professional.