For couples who are at risk of having a baby with a serious genetically inherited condition, the options are:
• To have the baby, test to see if it has the condition (post-natal screening);
• To test the foetus for the condition during pregnancy (pre-natal diagnosis);
• To create an embryo outside the body and test it for the condition.
Assisted reproduction techniques and human genome mapping have made it possible to take a cell out of a 2-3 day old embryo, when it is at the 4-8 cell stage and test the cell for the presence of various genes.
This technique is called pre-implantation genetic diagnosis (PGD) or embryo biopsy and in the UK it can be done legally if it is the interest of the embryo to do so. For example parents may wish to test the embryo for genetic conditions, such as cystic fibrosis or Huntington's disease.
It is ethically more problematic when this type of genetic testing is done to try to create a baby who can be a tissue donor for another person, for example a sick sibling or to select for other traits at the request of the parents.
Pre-implantation genetic diagnosis (PGD) or embryo biopsy