Guidance

Your antenatal blood test result: you are a haemoglobin D carrier

Updated 2 October 2020

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.

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You should read this information if the result of your antenatal screening blood test for sickle cell and thalassaemia (SCT) shows you are a haemoglobin D carrier. Some people call this ‘having a trait’.

Being a carrier

Being a carrier does not make you ill. You will not develop a haemoglobin condition that needs treatment but it is important to know that you can pass the haemoglobin D 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 haemoglobin D gene from your other biological parent.

There are different types of haemoglobin D. The most significant type is haemoglobin D^Punjab (or Hb D^Punjab), which is also called Hb D^{Los Angeles}. Further testing may be needed to identify the type of haemoglobin D gene you carry.

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.

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 the baby’s biological father has 2 usual haemoglobin genes (AA), there is a 2 in 4 (50%) chance your baby will be a haemoglobin D 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 types of haemoglobin gene 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. If the baby’s biological father is a sickle cell carrier (haemoglobin AS), and you carry haemoglobin D^Punjab there is a 1 in 4 (25%) chance that your baby could inherit sickle cell disease (Hb S D^Punjab). This is a serious health condition which requires specialist care and treatment.

If the baby’s biological father is also a haemoglobin D carrier (haemoglobin AD), there is a 1 in 4 (25%) chance that you could have a baby who only has haemoglobin D (Hb DD), and no haemoglobin A. This is not a serious condition and does not need any treatment.

Sickle cell disease

People with sickle cell disease have red blood cells that can become misshapen when 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 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 haemoglobin D carrier

• contact a specialist SCT centre where you can get free information and advice to help you understand the implications of being a haemoglobin D 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 haemoglobin D 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 could be written as haemoglobin D carrier or Hb AD. The letter A represents your usual haemoglobin A gene. The letter D represents your haemoglobin D gene.

A superscript (the smaller letters) to the right of the letter D represents the type of haemoglobin D gene. For example D^Punjab or D^{Los Angeles}.

More information

For more information see:

• NHS UK
• Sickle Cell Society E: [email protected] T: 0208 9617795

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.