Tim Child
Fellow in Reproductive Medicine in the Nuffield Department of Obstetrics & Gynaecology, University of Oxford
7.9 million children are born worldwide each year with serious birth defects as a result of inherited genetic conditions. Pre-implantation genetic diagnosis enables those with an inheritable condition to avoid passing it on to their children by checking the genes of an embryo.
At present, women at high risk of carrying a child with a genetic disease are offered tests during pregnancy. However, should they come back with positive results, parents face the agonizing decision of whether to terminate a pregnancy or care for a child who has a life-limiting or even terminal medical condition.
For prospective parents known to be carrying a disease, pre-implantation genetic diagnosis (PGD) could offer a ray of hope. The procedure follows normal IVF steps to collect and fertilise eggs. The embryos are then grown in a laboratory for 3-6 days when they consist of between 8 and 200 cells. A biopsy is performed of one or more cells to see if they contain the gene that causes the genetic condition. The embryo unaffected by the condition is transferred to the womb to allow it to develop.
PGD has been practiced for more than 20 years, but as IVF has become more refined so the PGD procedure has also become more accurate. In the last year alone, 533 women received the treatment, and 149 healthy babies were born as a result.
