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This short animation explains screening for sickle cell and thalassaemia in pregnancy.

1. Purpose of screening

We screen for sickle cell and thalassaemia in pregnancy to find out if you carry the genes for either of these conditions. This lets us know if you are likely to pass them on to your baby.

2. About these conditions

Sickle cell disease (SCD) and thalassaemia are serious inherited haemoglobin conditions. Haemoglobin is the important part of the blood that carries oxygen around the body. People who have these haemoglobin conditions will need specialist care throughout their lives.

People with SCD can have attacks of severe pain and get serious infections. They can also have anaemia (when their bodies have difficulty carrying oxygen). Babies with SCD can receive early treatment. This includes vaccinations and antibiotics to reduce severe illness and infections.

People with thalassaemia can be anaemic. They may need a blood transfusion every 3 to 5 weeks, injections and medicines throughout their lives.

The screening can also find less common and less serious haemoglobin conditions.

SCD and thalassaemia are inherited conditions. This means they are passed on from biological parents to children through unusual haemoglobin genes. Genes are the codes in our bodies for things such as eye colour and blood group. Genes work in pairs. For everything that we inherit, we get one gene from our biological mother and one from our biological father.

People only have SCD or thalassaemia if they inherit 2 unusual haemoglobin genes. One will come from their biological mother and one from their biological father. People who inherit just one unusual gene are known as ‘carriers’ (some people call this having a ‘trait’). Carriers are healthy and do not have the condition. The only time carriers may experience health problems is in rare situations where their bodies might not get enough oxygen. For example, if they were having surgery under an anaesthetic.

Anyone can be a carrier of an unusual haemoglobin. However, carriers are more common among people with family origins in certain parts of the world. These include Africa, the Caribbean, the Mediterranean, South and South East Asia, and the Middle East.

When both biological parents are carriers, the baby has:

• a 1 in 4 (25%) chance of not having the condition
• a 1 in 4 (25%) chance of inheriting both unusual haemoglobin genes and having the condition
• a 2 in 4 (50%) chance of inheriting 1 unusual haemoglobin gene and being a carrier

Diagram showing the chances of a baby inheriting a haemoglobin condition when both biological parents are carriers.

3. The screening test

Screening in pregnancy involves completing a Family Origin Questionnaire (FOQ) and having a simple blood test. It is best to have the blood test before you are 10 weeks pregnant.

The FOQ is a questionnaire about your family origins and those of the baby’s biological father. It goes back at least two generations.

The FOQ aims to find out if you or the baby’s biological father have family origins in countries where SCD and thalassaemia are more common.

All pregnant women in England are offered a blood test to check for thalassaemia. However, not all women are automatically offered a blood test to check for sickle cell. The screening for sickle cell is offered if the FOQ suggests a higher chance of being a sickle cell carrier. It may also be offered if you live in areas where haemoglobin conditions are more common.

You can ask to have the blood test even if your FOQ does not suggest you have a high chance of being a carrier.

4. Safety of the test

The screening test cannot harm you or your baby. However, it is important to consider carefully whether to have this test or not. The screening test may provide information that means you have to make further important decisions. For example, you may be offered further diagnostic tests. These could include chronic villus sampling (CVS) or amniocentesis.

5. Screening is your choice

You do not need to have the screening test. Some people want to find out if their baby has SCD or thalassaemia and some do not.

6. Not having the test

If you choose not to have the screening test in pregnancy, your baby can have screening for SCD as part of the newborn blood spot screening test. This is taken at 5 days of age.

7. Possible results

The screening test will tell you if you have a haemoglobin condition. It will also tell you if you are a carrier or not.

8. Diagnostic tests (chorionic villus sampling or amniocentesis)

Diagnostic tests give a definite answer. They test cells from the placenta or fluid surrounding your baby.

If you are a carrier of a haemoglobin condition, your baby’s biological father will be offered a blood test. If your baby’s biological father is also a carrier, you will be offered diagnostic tests. These will find out if your baby has the condition.

If your baby’s biological father is not available and you are a carrier, you will be offered a diagnostic test.

About 1 out of 200 women (0.5%) who have a diagnostic test will miscarry because of the test. It is up to you whether you have the diagnostic test.

There are 2 types of diagnostic test: chorionic villus sampling (CVS) and amniocentesis.

8.1 Chorionic villus sampling (CVS)

This is usually done from 11 to 14 weeks of pregnancy but can be done later. A fine needle is used to take a small sample of tissue from the placenta. The needle is usually put through the woman’s abdomen (tummy). The cells from the placenta can be tested for SCD or thalassaemia.

8.2 Amniocentesis

This is usually done after 15 weeks of pregnancy. A fine needle is used to collect a small sample of the fluid surrounding the baby. The needle is passed through the woman’s abdomen (tummy). The fluid contains some of the baby’s cells, which can be tested for SCD or thalassaemia.

9. Results from the diagnostic test

If the result shows that your baby has SCD or thalassaemia, you will be offered an appointment with a genetic counsellor. They can explain what this means for your baby and what your options are.

Some conditions are more serious than others. Some women decide to continue with the pregnancy. Others decide they do not want to continue with the pregnancy and have a termination.

If you are faced with this choice, you will get further information and support from healthcare professionals to help you decide. Information is also available from support organisations.

If the test shows that 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.