Healthy babies born using new genetic egg screening technique

Healthy babies born using new genetic egg screening technique

Four women have given birth to healthy babies after having their eggs genetically screened using a technique that offers new hope to childless couples.

The success could help women who have failed to conceive with the help of IVF to have babies. All were taking part in a pilot study testing a new method of looking for chromosomal abnormalities in eggs.

The technique, called comparative genomic hybridisation (CGH) by microarray, could also make it easier for women to give birth later in life when there is less chance of becoming pregnant.

But doctors involved in the trial stress that the technique can only help them identify viable eggs - it does nothing to improve the chances of producing high quality eggs in the first place.

The European Society for Human Reproduction and Embryology (Eshre) today announced that women at two centres in Bonn, Germany, and Bologna, Italy, had given birth to healthy babies after undergoing array CGH.

The German patient, aged 34, gave birth to twin girls in June. Three months later the 39-year-old woman in Italy gave birth to a baby boy. Later it was revealed that two more women aged 37 at the Bonn centre had given birth to singleton babies in August. A number of other women from the total of 41 taking part in the study are said to be at advanced stages of pregnancy.

Unlike other screening methods, CGH tests all 23 pairs of chromosomes in a cell, not just a limited number. It looks at the two polar bodies - incomplete daughter cells produced during cell division containing unwanted copies of a woman's chromosomes.

Although the polar bodies are never fertilised, the chromosomes they contain are an exact copy of those in the egg before and at the time of fertilisation. Studying the polar bodies therefore gives doctors a picture of the internal genetic state of a woman's eggs.

Although it focuses on female infertility, 95 per cent of chromosomal abnormalities affecting birth are found in women. The study, organised by an Eshre task force, provides proof in principle that CGH works.

More extensive trials on selected populations of patients are now needed, but doctors believe the technique might become part of clinical practice within two or three years.

Eshre chairman Professor Luca Gianaroli said: 'We have learned from more than 30 years of IVF that many of the embryos we transfer have chromosome abnormalities.

'indeed, it's still the case that two out of every three embryos we transfer shall fail to implant as a pregnancy, many of them because of these abnormalities.

'The whole world of IVF has been trying to find an effective way of screening for these abnormalities for more than a decade, but results so far have been disappointing with the technology available.

'Now we have a new technology in array CGH and our hopes are that this will finally provide a reliable means of assessing the chromosomal status of the embryos we transfer.' One advantage of the technique is that tests are carried out on eggs, not embryos due to be implanted into an IVF patient's womb.

This offers countries such as Germany which forbid embryo analysis and freezing a legal method of pre-implantation genetic screening.

Dr Markus Montag, one of the trial researchers from the University of Bonn, said the 34-year-old mother from his centre had been through a number of failed IVF attempts.

'She had several transfers, but never conceived,' he said. 'That meant something was going wrong.'

The average age of patients in the study was 40, well past a woman's most fertile years. But Dr Montag said women should not be encouraged to delay motherhood for the sake of their lifestyles or careers in the belief that techniques such as CGH can get them pregnant.

'Women should not wait until their 40s,' he said.

'Egg selection only works if there is something there to select. If a woman's oocytes (eggs) are all bad, she is not going to succeed with IVF.'

He thought the technique would be useful for women experiencing repeated implantation failure or who suffer from chromosomal abnormalities that can lead to birth defects and miscarriages.

Results validating the accuracy of the pilot study analysis were presented at Eshre's annual meeting in Rome in June.

They showed that complete chromosomal testing with array CGH can be completed within 12 to 13 hours. Reliable identification of the chromosomal state of an egg was possible in 90 per cent of cases.

A British woman became the first in the world to give birth after array CGH in 2009. The 41-year-old women gave birth to a baby boy named Oliver after undergoing 13 cycles of IVF without success.

She was one of a number of women with a poor prognosis treated by the Care Fertility Group in Nottingham.

Dr Simon Fishel, managing director of Care Fertility Group, said: 'It is gratifying that Care's ongoing success with this technology has been replicated. However, EHSRE is undertaking a 'controlled' study, and it is important for all the data of that study to be published so practitioners can assess the value of the study as a whole - this particular announcement does not yet move forward into widespread use the prospects for our exciting technology.'

Article: 15th October 2010

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Posted: 16/10/2010 14:02:02


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