Sickle cell disorder and thalassaemia major are serious, inherited blood disorders. They affect haemoglobin, a part of the blood that carries oxygen around the body. People who have these conditions will need specialised care throughout their lives. There are other, less common, haemoglobin disorders but many of these are not as serious.

People with sickle cell disorder:

• 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 their lives

People with thalassaemia major:

• are very anaemic
• need blood transfusions every four to six weeks
• need injections and medicines throughout their lives

For all of these reasons, it is strongly recommended that you are screened. However, you can choose not to be tested and your choice will be respected.

How are sickle cell and thalassaemia passed on?
Sickle cell and thalassaemia are inherited disorders that are passed on from parents to children through unusual haemoglobin genes. People only have these disorders if they inherit two unusual haemoglobin genes, one from their mother and one from their father. People who inherit just one gene are known as carriers (some call this having a trait). Carriers are healthy and do not have the disorder. However, if a carrier has a baby with someone who is also a carrier, or who has one of the disorders, there is a chance that their baby could inherit a disorder.

Who can be a carrier?
Anyone can be a carrier. However, it is more likely that you will carry the unusual gene if you or your ancestors came from places where malaria has been common. This is because being a carrier can help protect people against malaria. This means you are more likely to be a carrier if your ancestors came from the Mediterranean (for example Cyprus, Italy, Portugal and Spain), Africa, the Caribbean, the Middle East, India, Pakistan, Bangladesh, Sri Lanka, South America or south and south-east Asia.

Screening for sickle cell and thalassaemia
Screening involves a simple blood test. The best time to have the test is before you are 10 weeks pregnant. All pregnant women are offered a blood test for thalassaemia. You will not always be offered a blood test for sickle cell anaemia. You may be given a questionnaire to find out where your family - and the family of your baby's father - come from. If this shows you are at low risk, you may not be offered the blood test for sickle cell. You can always ask for the test if you want.

If the blood test shows that you are a carrier, the baby's father will be invited for a test. If he is also a carrier, your baby may inherit a disorder, may be a carrier, or may not be affected.

These tests early in your pregnancy give you the chance to talk to a counsellor and find out more about the disorders and the care available. If you want to, you can have another test to confirm whether your baby has one of the disorders (see amniocentesis and chorionic villus sampling).

If the test shows that you are a carrier, there is a chance that other family members could be carriers too. You may want to encourage them to ask for a test, especially if they are planning to have a baby.

Although people who are carriers of sickle cell anaemia are healthy, they can experience some problems in rare situations where their bodies might not get enough oxygen (for example, when having an anaesthetic before an operation or if they go deep-sea diving). Knowing that you are a carrier can help you manage these situations. However, people who carry thalassaemia or other unusual haemoglobin genes do not experience these problems.

Why should the baby's father have a test?
Babies can only inherit the disorders if both parents carry the unusual gene. So if you are a carrier, it is important to find out whether the baby's father is also a carrier. If he is not available or does not want to have a test, you may be offered another test to find out whether your baby has sickle cell anaemia or thalassaemia (see amniocentesis and chorionic villus sampling).

If the baby's father is also a carrier
If you and the baby's father both carry the gene for sickle cell anaemia, thalassaemia or another haemoglobin disorder, for each baby you have there is:

• a 25% chance that your baby will not be affected (that is, it will not have or carry a disorder)
• a 50% chance that your baby will be a carrier
• a 25% chance that your baby will have a disorder

If both you and the baby's father are found to be carriers, you will be offered a test to confirm if your baby is affected. This test is either an amniocentesis or a chorionic villus sample (CVS).

Other inherited conditions

Cystic fibrosis: Cystic fibrosis is an inherited disease which affects vital organs in the body, especially the lungs and digestive system, by clogging them with thick sticky mucus. The sweat glands are usually also involved. The disease is inherited, and both parents must be carriers of the gene variation for a baby to be born with cystic fibrosis. Testing is offered in pregnancy if there is a family history of conditions such as cystic fibrosis or Duchenne muscular dystrophy.

Sachs disease: Testing for Tay Sachs disease should be offered if you or your partner is of Ashkenazi Jewish origin and you consider yourself or your partner at risk.