January 27, 2009
UK Fertility Clinic Screens Eggs For Safe IVF
A fertility clinic in Nottingham, England has announced the world's first pregnancy using a new technique that screens eggs for abnormalities that cause in vitro fertilization (IVF) to fail.
Researchers from the CARE Fertility clinic have found a way of extracting a "spare" set of chromosomes inside the egg and rapidly analyzing them"”a technique that could have the potential to significantly improve couples' chances of having successful treatment.The study suggests chromosomal abnormalities in the eggs could be the main reason why two out of three women fail at each attempt at IVF.
For conception, the 23 chromosomes in the egg that contain the woman's share of the genetic code are matched with the other half from the sperm after fertilization. The spare chromosomes in the egg are found near its edge in what is known as the polar body.
The team at the CARE fertility Clinic has developed a technique called array CGH (Comparative Genomic Hybridization) where a laser cuts a hole in the edge of the egg and the polar body is sucked out using a pipette.
The polar body contains chromosomes inside that are a mirror image of those left in the egg, and by analyzing what is in the polar body, scientists can work out what is left behind in the egg without disturbing it.
If there is a chromosome missing from the egg, then any subsequent embryo will fail despite its healthy appearance under a microscope.
But if an extra chromosome is discovered, it could lead to a miscarriage or a pregnancy with an inherited genetic disorder.
Scientists in the U.S. announced in 2007 that 18 women had given birth after having their eggs screened with CGH, with another eight pregnant, BBC News reported.
However, in those cases, the subsequent embryos had to be frozen and re-implanted later because the results of the screening took five days. But with the array CGH technique, the results come back within 24 hours, making IVF possible within the same cycle of treatment.
The moral and religious objections some couples feel about creating and testing embryos that may be destroyed also no longer apply.
The technique could help many women who have complications getting pregnant, according to Dr. Simon Fishel, director of the CARE fertility group.
"We know that at least half the eggs and embryos produced are wasted due to chromosomal abnormalities. If we could chose those with normal chromosomes logic tells us we double the chances of pregnancy and that's what we hope," said Fishel.
Fishel also suggests it could help reduce the number of twins and triplets associated with fertility treatment.
"Ultimately we could reach the holy grail of one cycle of IVF, one egg, one embryo and one baby."
In the UK, over 35,000 women undergo IVF each year and just one in three cycles is successful. But it is far too early to know if array CGH is going to transform success rates.
"We need further research in this area so questions of reliability, efficacy and safety can be fully answered," said Stuart Lavery, a consultant gynecologist and director of IVF at Hammersmith Hospital in London.
The research is exciting and promising, according to Tony Rutherford, chair of the British Fertility Society, but he also urged caution.
"The widespread use of this technology should await the outcome of such research to ensure we know which patients might benefit.
He said groundbreaking news about techniques that seem to offer great hope often fail to live up to expectations when applied in widespread clinical practice.
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