What is thalassaemia?
Thalassaemia is an inherited (genetic) blood disorder that affects the body's ability to make healthy haemoglobin, the iron-rich protein found in red blood cells. Haemoglobin is needed to carry oxygen to all parts of the body, and carbon dioxide to the lungs to be exhaled.
What types of thalassaemia are there?
There are many types of thalassaemia. The symptoms and severity depend on how many genes have mutated, and which part of the haemaglobin is affected.
Haemoglobin is made up of two matching chains of proteins: the alpha chain and the beta chain. The two main types of thalassaemia are:
- Alpha thalassaemia, which is caused by a mutation of up to four genes. This is most likely to affect you if you are of African, Asian or Middle Eastern descent.
- Beta thalassaemia, which can be caused by more than 200 gene mutations, and is much more common than alpha thalassaemia.
You are most likely to have it if your ancestors are from Mediterranean countries, the Middle East, Asia or Africa. In the UK most cases are in families of Indian, Pakistani or Bangladeshi origin.
Within the above types, there are the following sub-types:
- Thalassaemia minor, which is caused by inheriting the thalassaemia genetic disorder from only one parent. If you have thalassaemia minor you are a carrier of the disease, but won't usually have health problems. Beta thalassaemia minor is the most common thalassaemia and affects about 210,000 people in England.
- Thalassaemia major are more serious blood disorders which mean you inherit the defective gene from both your parents. Beta thalassaemia major is more common in babies and children than alpha thalassaemia major. This is because, sadly, few babies with alpha thalassaemia major survive beyond pregnancy or birth.
You'll know if you have beta thalassaemia major, because you’ll have had health problems related to the disease and regular treatments and medication.
However, it's quite common for people with thalassaemia minor not to know they have it, because there are usually no symptoms. Pregnancy could be when you find out for the first time that you have thalassaemia minor and are a carrier of it.
How do I find out if I am a thalassaemia carrier?
Your midwife or doctor will ask you to complete a family origin questionnaire. If you or your baby's father are deemed to be in a high-risk group you will be offered a blood test in early pregnancy. This will be by the time you are 10 weeks pregnant.
If you are planning to get pregnant and are worried that you or your partner may be a carrier, you can ask your GP for blood tests before you conceive.
If you already know that you or your partner has thalassaemia, and are planning a family, or expecting a baby, the other parent will need to have a blood test too. This will assess the risk of your baby inheriting the condition.
If you have a positive test, tell the rest of your family. One of your relatives may be planning to have a baby and will need to be tested too. And carrying thalassaemia can leave you short of oxygen in some situations, such as under general anaesthetic. So a relative who is planning to have surgery may need to know.
You can ask for a test at any stage, either from your GP, or at a specialist sickle cell and thalassaemia centre. Find your nearest centre here.
How will thalassaemia affect my pregnancy?
It depends on the type of thalassaemia. Some types of thalassaemia make it difficult to conceive, and require specialist consultant care. Others have less serious effects on fertility and pregnancy.
- Alpha thalassaemia minor can cause anaemia in pregnancy, particularly if you carry two mutated genes.
- Alpha thalassaemia HbH disease happens when you have three mutated alpha chain genes. It causes severe anaemia and requires blood transfusions.
- Beta thalassaemia minor may result in anaemia due to a lack of iron.
- Beta thalassaemia major makes it difficult to become pregnant without fertility treatment. Once you conceive, you are likely to have complications during your pregnancy. Your organs, which are already under strain, will have the extra demands of growing a baby. Your transfusion and medication needs will probably change as your pregnancy progresses.
You may be advised to book a hospital birth if thalassaemia has led to complications, such as anaemia. Beta thalassaemia major can affect how your bones grow, which could make a vaginal birth difficult. So planning your birth at an obstetric-led unit is recommended, in case you need a caesarean.
If I'm pregnant and have thalassaemia, what should I do?
If you weren't referred before you conceived, your GP should refer you to a doctor that specialises in blood disorders (haematologist) for assessment. Depending on the type of thalassaemia you have, you may be cared for by a specialist team throughout your pregnancy.
Whether you have thalassaemia or are a carrier, your baby will benefit from you taking 5mg of folic acid daily. This is because thalassaemia may increase the risk of your baby developing a neural tube defect, such as spina bifida. Taking a high dose of folic acid daily reduces the risk.
If you have thalassaemia minor, you may be more prone to iron deficiency (anaemia). If you become anaemic, you will need to take iron supplements. However, beta thalassaemia minor can affect blood test results during pregnancy and indicate that your iron stores are low when they're not.
If you have beta thalassaemia minor, you'll have extra tests of your ferritin levels to confirm that you're iron-deficient before you take iron tablets.
How do I find out if my unborn baby has thalassaemia?
If you and your partner have been diagnosed with thalassaemia, there are ways to find out if your baby has inherited it:
- Chorionic villus sampling involves taking a small sample of the placenta for DNA testing at about 11 weeks to 14 weeks of pregnancy.
- Amniocentesis, in which the amniotic fluid surrounding your baby is tested at between 15 weeks and 18 weeks of pregnancy.
- Fetal blood sampling, during which a blood sample is taken from the umbilical cord at about 18 weeks to 21 weeks.
When a baby is affected by alpha thalassaemia major and has a very low chance of survival, some parents consider ending the pregnancy. This is because the baby may not have a good quality of life, even if they have complex treatments.
This is a difficult decision, so an early diagnosis will be better for you and your family. The results are confidential, and if they are positive, a counsellor will explain your options before you and your partner make a decision.
For more information about screening tests in pregnancy, see the NHS screening programme.
Will my baby have thalassaemia?
Thalassaemia is passed down through families and is carried on a recessive gene. This means that your baby won't automatically inherit the disorder, in much the same way that eye or hair colour of a parent isn't always shared by the child.
If your baby has one parent with thalassaemia minor, he has a 50 per cent chance of inheriting the gene defect and being a carrier like his parent. If both your baby's parents have thalassaemia minor, he could have a double dose of the gene, and have the more severe thalassaemia major.
However, it is more likely that your baby will be born healthy, either as a thalassaemia carrier, or completely free of the disorder.
Each child born to parents who are both thalassaemia carriers has a:
- one in four chance that they will be neither carriers, nor have the disease
- one in two chance of being a symptom-free carrier
- one in four chance of having the more severe thalassaemia major
If you and your partner are at risk of having a baby affected by thalassaemia, you may choose to conceive using pre-implantation genetic diagnosis (PGD). This will take place at a fertility clinic to make sure that only healthy embryos are implanted as part of in vitro fertilisation (IVF).
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