When children have a life threatening illness, parents are often prepared to consider any measure that could save them. Having another child who could donate bone marrow or other cells may be a lifesaver. In December 2001 the UK Human Fertilisation and Embryology Authority (HFEA) decided in principle to allow HLA (human leukocyte antigen) typing to be used with preimplantation genetic diagnosis (PGD) for serious genetic disease. Parents at risk of transmitting genetic diseases could use PGD, not only to select (...) embryos free of disease, but also to choose those with the best tissue match to the dying sibling. The HFEA’s agreement to selection by HLA typing was subject to strict conditions1 and each individual request must be considered by the HFEA. In the following months, the HFEA considered two applications, it approved one and the other (for a non-genetic condition) it rejected. Interestingly, both decisions attracted criticism, the first for being too liberal and the second for being too conservative. The first case concerned Zain Hashmi who had beta thalassaemia. His parents wanted PGD to avoid the birth of another affected child and also to select embryos most likely to produce a baby who would be a compatible donor. They hoped to use stem cells from the umbilical cord blood to produce bone marrow for the transplant, thus the future child would not undergo any invasive, painful, or risky procedures. Approval was given by the HFEA for this case. In the second case, Charlie Whittaker had Diamond-Blackfan Anaemia (DBA), a rare life threatening blood disorder. Although some children with DBA inherit this condition from carrier parents, his parents were not actually carriers. Preimplantation genetic diagnosis was not needed, therefore, to avoid the birth of an affected child but the couple wanted it solely to provide …. (shrink)