Guidance

Your antenatal blood test result: you are a sickle cell carrier

Updated 2 October 2020

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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 because the result of your antenatal screening blood test for sickle cell and thalassaemia (SCT) shows that you are a sickle cell carrier. Some people call this ‘having a trait’.

Being a carrier

Being a carrier does not make you ill. You will not develop sickle cell disease but it is important to know that you can pass the sickle cell gene on to your baby. If the 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.

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

If the baby’s biological father has an unusual haemoglobin gene it is important to identify the type of gene and the chance of your baby inheriting a serious haemoglobin condition. For this reason, we will also invite the biological father for screening. He will only know he carries a gene for unusual haemoglobin if he has a blood test to check his haemoglobin type.

If the test shows the biological father is a carrier of an unusual haemoglobin gene you will be offered specialist counselling and if necessary, diagnostic testing.

Rare health issues

There are rare occasions when you should take extra care because of your carrier status. If you need a general anaesthetic, you should tell medical staff you are a sickle cell carrier.

This is so they can make sure you always get enough oxygen. You should check that there is full medical back-up anywhere you have a general anaesthetic, including for dental treatment.

In addition, if you take part in any form of intense sporting activity, you should:

  • make sure you drink plenty of fluids
  • avoid extreme exhaustion
  • are never short of oxygen

Please let your healthcare professional know 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

There are a number of different haemoglobin conditions your baby could inherit. Some are more serious than others. The type and severity of the condition depends on the types of haemoglobin gene you and your baby’s biological father have.

The most serious condition is sickle cell disease. People who have sickle cell disease need specialist care and treatment throughout their lives.

Chances of inheriting a condition

One biological parent is a carrier and the other is not

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

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

Both biological parents are carriers

If the baby’s biological father is also a carrier, there is a 1 in 4 (25%) chance your baby will inherit a haemoglobin condition. The seriousness of the condition will depend on what haemoglobin genes are inherited.

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 genes (AA).

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

Inherited haemoglobin conditions

Haemoglobin conditions are blood diseases inherited from both biological parents.

There are a number of haemoglobin conditions, but the type of condition your baby could inherit will depend on what type of haemoglobin genes both biological parents have. Some conditions are more serious than others.

One of the most serious conditions is called sickle cell disease. There are different types of sickle cell disease, but the most serious type is sickle cell anaemia (Hb SS), which occurs when both biological parents are sickle cell carriers.

If one biological parent is a sickle cell carrier, and the other biological parent has an unusual haemoglobin gene such as beta thalassaemia or haemoglobin C, this could cause a different type of sickle cell disease. Your healthcare professional can discuss this with you, so that you understand exactly what condition your baby could inherit, and how serious it is.

People who have sickle cell disease will need specialist care and treatment throughout their lives.

Sickle cell disease

People with sickle cell disease have red blood cells that can become misshapen as they release oxygen around the body. This can block small blood vessels.

People with sickle cell disease:

  • can have attacks of very severe pain
  • can get serious, life-threatening infections
  • are usually anaemic
  • need medicines and injections when they are children and throughout the rest of their lives to prevent infections

Next steps and choices

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

Newborn screening

All babies are offered a newborn blood spot screening test 5 days after their birth. This test will screen for sickle cell disease .

You can also:

  • let your GP or healthcare professional know you are a sickle cell carrier

  • contact a specialist SCT centre where you can get free information and advice to help you understand the implications of being a sickle cell carrier

  • organise for any other children you have to be tested if needed with help from your GP or SCT centre

Other family members

As you are a sickle cell 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.

It is equally important for men and women to be tested. Anyone can ask for a test at any time from their GP or from a specialist SCT centre.

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 the baby’s biological father and be referred to a specialist counsellor.

How your test result is written

Your result is written as sickle cell carrier or Hb AS. The letter A represents your usual haemoglobin A gene. The letter S represents your sickle cell haemoglobin gene

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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