Find out more about 'saviour siblings'
Publication Date:22/05/2008
You may have heard that the law is being changed to allow doctors to help couples create so-called ‘saviour siblings’: babies that can help cure serious illnesses in their older brothers or sisters. But how does it work, and what can it be used for? We take a look at the science and explain what happens.
What are ‘saviour siblings’?
For many years, doctors have been able to successfully treat children with certain serious diseases using bone marrow transplants. Bone marrow is a spongy material inside our bones, which makes different types of blood cells. If the bone marrow is damaged by illness, it can no longer make the blood cells the body needs.
A bone marrow transplant involves taking special cells, called stem cells, from the bone marrow of a healthy person and injecting them into the bone marrow of the sick child. Stem cells are able to produce new, healthy blood cells.
More recently, doctors have started using stem cells from the umbilical cords of newborn babies in a similar way.
But these treatments only work if the bone marrow or stem cells being used are a close match for the cells of the child being treated. The best chance of matching cells comes from a brother or sister (sibling), because they will share the same mixture of genes from the mother and father.
So it’s not new for doctors to use tissue from the brother or sister of a sick child in the hope of curing a serious disease. But since 2001 doctors have been able to test the cells of embryos created by IVF, to see whether they are a match for the sick child. This means that, in theory, parents could have babies they have chosen specifically to help their sick child.
These children have been called ‘saviour siblings’ because they may be able to save the life of their sick older brother or sister.
What conditions can be helped by ‘saviour siblings’?
The types of conditions where umbilical cord stem cells or bone marrow is used are mostly blood diseases. These include problems with the immune system, and a type of incurable anaemia where the bone marrow doesn’t produce red blood cells. Also, if a child has leukaemia (cancer of the blood) they may need a bone marrow or stem cell transplant to replace the cancerous cells with healthy cells.
What happens to create ‘saviour siblings’?
It’s quite a complicated process. Here’s what needs to happen:
- The sick child’s doctors have to agree that stem cells or bone marrow from a brother or sister is the only option for treating the child’s illness.
- The child’s parents have IVF. They need to produce a lot of embryos to test. So the woman needs to take drugs to make her produce more eggs than normal. The eggs are fertilised by the man’s sperm in the laboratory.
- The doctors wait till the embryos are three days old. At this stage they usually consist of eight cells each. They remove one cell from each embryo.
- The cell is tested to see if it’s a match for the sick child. If the child has an inherited disease, the cell will also be tested to try to be sure it doesn’t have the same disease.
- If an embryo is a good match, it will be implanted into the woman’s womb. If this is successful, the embryo will grow into a healthy baby.
- When the baby is born, doctors will collect blood from the umbilical cord. This blood may be given to the sick child as a blood transfusion. Or, if the sick child needs a bone marrow transplant, the doctors will wait until the baby is old enough to take some of its healthy bone marrow and give it to the sick child.
How well does it work?
We don’t know. This is a new technique and it has only been tried a few times. Many things can go wrong:
- The embryos produced by IVF may not be a good match. IVF is a difficult and expensive process. Parents may not be able to go through it enough times to product a matching embryo.
- IVF may not work. The embryo put into the woman’s womb might not grow into a healthy baby.
- The test may not be completely accurate, so the baby might not be a good match after all.
Because it is such a new technique, we don’t know whether there might be long-term effects for the baby. So far, it seems that embryos that carry on developing after having a cell removed grow into normal children.
Why are MPs changing the law?
There are strict laws governing what fertility clinics can and can’t do. But science has moved on since these laws were passed in 1990. The current law doesn’t say whether fertility clinics can test embryos to create ‘saviour siblings’. Individual cases have been tested in the courts, and some clinics have been allowed to do testing, but only in these specific cases.
The bill being debated at the moment says that licensed clinics should be allowed to test embryos for tissue matching, to help produce a ‘saviour sibling’, so long as certain safeguards are met.
MPs have voted in favour of this part of the bill, which is likely to become law in April 2009.
From:
Department of Health, Human Fertilisation and Embryology Bill 2008, available at http://www.commonsleader.gov.uk/output/page2162.asp. Human Fertilisation and Embryology Authority: Report on pre-implantation tissue typing, July 2004, available at http://www.hfea.gov.uk/en/494.html. Human Genetics Commission, Pre-implantation Genetic Diagnosis, available at http://www.hgc.gov.uk/UploadDocs/Contents/Documents/PGD%20Template.doc.
News Archive
© BMJ Publishing Group Limited ("BMJ Group") 2007. All rights reserved
This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
