TWO million babies worldwide have been born following in vitro fertilisation, and the embryos of at least 1000 of these were screened for genetic diseases before implantation.
These successes were celebrated by fertility experts at a conference on pre-implantation genetics in London last month. And it is only the beginning: in the future more and more clinics will be offering pre-implantation genetic diagnosis (PGD) for an ever-growing range of diseases.
Until recently there were several obstacles in the way of the widespread use of PGD and its extension to new diseases. Standard genetic tests require relatively large amounts of DNA, extracted from millions of cells. But in PGD the tests have to be done on single cells taken from three-day-old embryos, and completed in time for the selected embryos to be transferred on day four or five.
That means special tests have had to be developed that work with such ...
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