Published January 2022
Contents
― Being a carrier
― Your baby
― Chances of inheriting a serious condition
― Inherited haemoglobin conditions
― Sickle cell disorder
― Next steps and choices
― Newborn Screening
― Other family members
― Future pregnancies
― How your test result is written
― More information
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. Because you have inherited usual haemoglobin A from one parent you are healthy.
There are different types of haemoglobin D. The most significant type is haemoglobin DPunjab (or Hb DPunjab), which is also called Hb DLos 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 if 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, invasive testing.
Please let your healthcare professional know if you:
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 disorder. People who have sickle cell disorder need specialist care and treatment throughout their lives.
One biological parent is a carrier and the other is not
If the baby’s biological father has two 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 two 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.
Haemoglobin conditions are blood disorders 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 disorder. There are different types of sickle cell disorders. If the baby’s biological father is a sickle cell carrier (haemoglobin AS) and you carry haemoglobin DPunjab , there is a 1 in 4 (25%) chance that your baby could inherit sickle cell disorder (Hb S DPunjab). 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.
People with sickle cell disorder 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 disorder:
If screening shows your baby could inherit a serious haemoglobin condition you will be offered specialist counselling and invasive testing.
All babies are offered a newborn blood spot screening test five days after their birth. This test will screen for sickle cell disorder.
You can also:
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 sickle cell thalaessaemia centre.
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.
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.
The smaller letters to the right of the letter D represent the type of haemoglobin D gene. For example DPunjab or DLos Angeles.
You can get more information from the following.
https://111.wales.nhs.uk/encyclopaedia/t/article/thalassaemia/