Guidance

Your antenatal blood test result: you are an alpha zero thalassaemia carrier

Published 22 February 2021

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Public Health England (PHE) created this information on behalf of the NHS. In this information, the word ‘we’ refers to the NHS service that provides screening.

You should read this information if the result of your antenatal blood test for sickle cell and thalassaemia (SCT) shows you are an alpha zero thalassaemia carrier and this has been confirmed by a genetic (DNA) test.

Being a carrier

Being a carrier does not make you ill. You will not develop a thalassaemia condition that needs treatment but it is important to know that you can pass alpha zero thalassaemia on to your baby.

If your baby’s biological father is also a carrier, together you could have a baby with a serious inherited condition. The chance is the same in every pregnancy.

Alpha zero thalassaemia is more common among people whose family origins are South East Asian or Southern Mediterranean (Sardinia, Greece, Turkey and Cyprus). If your baby’s biological father has family origins from one of these areas it is important to know his carrier status and he will be invited for screening. If the test shows the biological father is also an alpha zero thalassaemia carrier you will be offered specialist counselling and, if necessary diagnostic testing.

As an alpha zero thalassaemia carrier your red blood cells are smaller than usual and your haemoglobin level is lower than normal. This is different to iron deficiency anaemia. Always ask your healthcare professional to check your iron levels before taking iron supplements.

Haemoglobin is the substance in red blood cells that carries oxygen around your body. Being a carrier means you have inherited the usual haemoglobin A gene from one biological parent and alpha zero thalassaemia from your other biological parent.

Tell your healthcare professional if you:

  • became pregnant as a result of fertility treatment with donor sperm or a donor egg
  • have had a bone marrow or stem cell transplant
  • are pregnant as a surrogate

Your baby

If you and your baby’s biological father are both carriers, together you could have a baby with a serious inherited condition called alpha thalassaemia major (also known as Barts Hydrops Fetalis Syndrome).

Alpha thalassaemia major causes severe anaemia in the baby, resulting in restricted growth, and miscarriage or stillbirth.

Very occasionally, babies with alpha thalassaemia major survive to birth if they have blood transfusions in the womb. They will need blood transfusions throughout their life and there is a high risk of significant disabilities. If your baby is at risk, you can discuss the possibility of this treatment with your healthcare professional.

If your baby has inherited alpha thalassaemia major there are also health implications for you during pregnancy and at delivery. You will be monitored closely in pregnancy and your healthcare professional can give you more information about this.

Chances of inheriting a serious condition

One biological parent is a carrier and the other is not

If your baby’s biological father has usual haemoglobin A, there is a 2 in 4 (50%) chance your baby will be a carrier (like you) and a 2 in 4 (50%) chance they will have usual haemoglobin A.

See diagram below. These chances are the same in every pregnancy for this couple.

Both biological parents are carriers

If your baby’s biological father is also a carrier, there is a 1 in 4 (25%) chance your baby will inherit a serious haemoglobin condition.

There is also a 2 in 4 (50%) chance your baby will be a carrier, and a 1 in 4 (25%) chance your baby will have usual haemoglobin A.

See diagram below. These chances are the same in every pregnancy for this couple.

Next steps

If screening shows your baby could inherit a serious haemoglobin condition you will be offered specialist counselling and prenatal diagnosis.

If the result shows that your baby has alpha thalassaemia major you will be offered an appointment with a specialist to discuss the choices for your pregnancy.

You can talk to your healthcare professional at any time if you have questions.

Future pregnancies

We recommend you tell your healthcare professional about your carrier status as early as possible in any future pregnancies.

It is important to test your baby’s biological father and be referred to a specialist counsellor.

Other family members

As you are an alpha zero thalassaemia carrier, other members of your biological family could be carriers too.

We recommend you talk to your parents, brothers, sisters, uncles, aunts and cousins, and encourage them to get a test before they start a family or have any more children. Showing them this information may help.

Free information, advice and testing can be arranged by contacting your GP or local specialist SCT centre.

How your test result is written

Your test result is written alpha zero thalassaemia carrier.

More information

For more information see:

The NHS Screening Programmes use personal information from your NHS records to invite you for screening at the right time. Public Health England also uses your information to ensure you receive high quality care and to improve the screening programmes. Find out more about how your information is used and protected, and your options.

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