Screening for sickle cell and beta thalassaemia

Explaining genetics and risk

One of the first tasks in counselling people who discover they are or their baby is a carrier is to explain the difference between being a carrier and having the condition. Many people are worried at first that they or the baby will be seriously ill and need reassurance that this is not so.

Having reassured people that being a carrier does not make them ill, a key task for professionals is to explain how recessive conditions such as sickle cell disorders and beta thalassaemia major are inherited and what the risks are of having a baby affected by the condition. Most people we talked to felt they had been given very good counselling to help them understand how the genes are passed on, and particularly valued the use of drawings or diagrams to demonstrate inheritance.

However, some people's responses showed that they had misremembered some information or had added their own meanings or interpretations. For example, one person identified the risk of two carriers having an affected child as 1 in 10 rather than 1 in 4, and several people who knew they were carriers used expressions such as 'I've got thalassaemia but it's not major'. One mother believed that having CVS in one pregnancy had, in some way, caused her daughter's beta thalassaemia major' 'She is like this because of that [CVS]… I think the needles that they put inside, or the sample they take, they take some flesh or something, I don't know.' Other examples included:

'I thought she [daughter who is a beta thalassaemia carrier] will have less blood from one side, maybe that's why she doesn't eat.'

'[Beta thalassaemia] is like a blood condition, like it happens in our Pakistan because of dirt, because of disease, that's why there is thalassaemia. Some people catch it.'

'We understood that one of us had got bad blood, as such, and one of us had got good blood.' 

'Normal blood cells are round, aren't they? Whereas sickle cell blood cells are spiky. So that hurts as it's going round your blood system.'

The National Screening Programme recommends avoiding use of the word 'trait' (meaning 'genetic characteristic') to describe carrier status but many people interviewed were using it. A particular problem is that 'trait' sometimes becomes confused with the word 'trace', giving people a misleading impression that it is something minor or insignificant. One woman explained she had been led to believe the presence of haemoglobin S was not permanent. The family thought that she couldn't be a sickle cell carrier because she was always getting malaria as a child, and being a carrier is thought to be protective against severe malarial infection, particularly in childhood. (However, carriers are still at some risk of malaria infection). 

It may help some parents to be told that being a carrier does have some health advantages. As well as protection against malaria, there is some evidence that being a beta thalassaemia carrier reduces the risk of coronary heart disease.

Understanding recessive inheritance is an important part of explaining why partner screening is recommended. Again, making it clear that carriers have no obvious symptoms and will not know whether they are carriers unless they are tested is essential. 

It is also important to explain that white people can also be carriers. Two black women with white partners had not been aware of this.

If both parents are found to be carriers, they will need counselling on the chances of having a baby with the condition or a baby who is also a carrier or unaffected and on the fact that the chances remain the same in each pregnancy. Explaining in practice what risks of 1 in 4 or 1 in 2 mean can be difficult, and each individual will make different personal assessments. One mother with SC disorder described her optimistic outlook, comparing her 1 in 4 risk of having a baby with sickle cell anaemia to the risk of being knocked down by a car (which is in fact many times lower). 

By contrast a man whose sister had died of beta thalassaemia major regarded it as unacceptable and even irresponsible to run a risk of 1 in 4 of having a baby with the condition.

Last reviewed December 2018.


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