Pre-Implantation Genetic Screening

In November 2006, the UK's first ever babies born after a pre-implantation genetic screening procedure, were delivered to their ecstatic parents.

Mr and Mrs Greenstreet carry the defective gene for Cystic Fibrosis (CF). They already had twins, five year old Lizzie and William. Their daughter Lizzie has CF.

CF is a life threatening condition which requires an extensive regimen to treat it, including daily physical therapy and the administration of various antibiotics.

The Greenstreets were not going to have any more children until they discovered pre-implantation genetic screening.

After the fertilisation of the embryos in a lab, a tiny sample of DNA is removed and analysed to see if the embryo has any genetic fault. Only the healthy embryos are put into the mother's womb. Mrs Greenstreet's healthy embryos were selected and put back.

She gave birth to twin boys, Freddie and Thomas, free from worry and knowing they did not have CF.

Professor Peter Braude, head of the department of women's health at King's College and clinical director of the pre-implantation genetic screening programme said: "PGS can make an enormous difference for some families who have repeatedly miscarried, lost children through serious genetic disease, or are living with a child suffering from a serious genetic disease.'

But some doctor's would disagree with him. This year, specialists from the British Fertility Society say that the technique makes no difference for women who have repeatedly miscarried, does not lessen the risk of miscarriage and does not improve rates of success in IVF.

Professor Richard Anderson said, 'It is clear there is no compelling evidence that PGS improves the clinical pregnancy rate, live birth rate, or that it reduces the miscarriage rate.'

He has suggested that any prospective patients just embarking upon IVF should be informed that there is no evidence that pre-implantation genetic screening works.

The advice for couples who have a genetically inherited condition remains unchanged. Pre-implantation genetic screening is still an effective way of ensuring any children born to them are not affected by the condition.

The Human Fertilisation and Embryology Authority is reviewing the guidelines to determine whether they will still offer this form of treatment routinely for couples having IVF who are over the age of 35 years.

Another professor, Alan Handyside, from the Bridge Centre Fertility Clinic in London, disagreed with Professor Anderson about the efficacy of the procedure to reduce miscarriage and said he was worried that the new guidelines would cause the authority to withdraw the clinic's licence to perform pre-implantation genetic screening.

As the majority of first trimester miscarriages are caused by a chromosome abnormality in the embryo, he argued that the screening technique could reduce miscarriages because they would be implanting embryos which were free from those abnormalities. If all of a couple's embryos were found to be defective, then they had the option of not using any of them, thus preventing a potential termination of pregnancy.

Triplets

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