Saviour Siblings
The term 'Saviour Sibling' is now commonly used to refer to a child created using PGD to act as a donor for an existing sick child. This may just mean taking blood from the umbilical cord, but if that's unsuccessful, other procedures may be necessary. In December 2010, the first tissue transplant from a 'Saviour Sibling' took place in the UK, showing how new this technology is. However, prior to PGD it was still possible to create a donor sibling - some couples just had sex in the hope that a new baby might be able to act as a donor. As such, the term 'saviour sibling' is somewhat vague.
In the UK, you can only use PGD in cases where there is a significant risk of the child having an inherited genetic disorder. As such, Saviour Sibling cases in the UK involve inherited genetic disorders. However, one UK family had a child who was very ill, but the disorder wasn't inherited, and they still wanted to create a donor sibling. They had to go to the US to do this.
So, a saviour sibling can be any child that acts as a donor to a brother or sister, but on this site we will limit this to cases where PGD was used to screen for a donor match.
