The appropriate extent of pre-implantation genetic diagnosis: health professionals' and scientists' views on the requirement for a 'significant risk of a serious genetic condition'.

If a couple knows or fears that they are at risk of having a child with a genetic condition or disease, they may seek in vitro fertilisation (IVF) treatment and pre-implantation genetic diagnosis (PGD). Although success cannot be guaranteed, the purpose of PGD is to enable parents to have a child without a genetic impairment and, in so doing, to avoid moral or other difficulties in the termination of an alreadybegun pregnancy. PGD can be performed when there is a ‘significant risk of a serious genetic condition being present in the embryo’, the criteria established by the Human Fertilisation and Embryology Authority (HFEA) and Human Genetics Commission (HGC). The technique involves genetic testing of a cell extracted from a six-to-tencell (day 3) embryo fertilised and grown in vitro. When a couple approaches a PGD clinic, they may find that the condition of concern to them is one for which the HFEA has already granted a licence