July 4, 2011
Risk Of Down’s Syndrome May Increase With IVF Procedure
Physicians are well aware that the chance of birthing a child with Down's syndrome increases with the age of the mother, especially for those over 35. Researchers are now also finding links between Down's syndrome and drugs used in in-vitro fertilization (IVF) for older women, BBC News reports.
UK researchers looking at 34 couples have discovered a link with IVF in older women disturbing the genetic material of her eggs. The magnitude of the risk is still unknown but it could also cause many other genetic conditions, not just Down's.
All of the women in the study were older than 31 years of age and had been given treatments to make their ovaries release eggs ready for their IVF procedure. When the researchers studied those now fertilized eggs they found some had genetic errors.
These errors could encompass a wide range of results from death of the child to the child being born with a genetic disease. A closer look at 100 of the faulty eggs revealed that many of the errors involved a duplication of a chromosome.
Often, the error resulted in an extra copy of chromosome 21, which causes Down's syndrome. But unlike "classic" Down's syndrome which is often seen in the babies of older women who conceive naturally, the pattern of genetic errors leading to Down's in the IVF eggs was different and more complex. This led the researchers to believe that it was the fertility treatment that was to blame.
Lead researcher Professor Alan Handyside, director of the London Bridge Fertility, Gynecology and Genetics Center, said more research was now needed.
"This could mean that the stimulation of the ovaries is causing some of these errors. We already know that these fertility drugs can have a similar effect in laboratory studies. But we need more work to confirm our findings," Handyside told BBC News.
If more tests back up their suspicions, doctors should consider being more cautious about using IVF treatments, he said.
At present, IVF clinics tend towards a wholesale approach by administering powerful hormones to prod follicles in the ovaries into producing eggs, AFP reports.
The eggs are harvested, fertilized in a lab dish and two or more early-stage embryos are then transfer to the uterus in the hopes that one will develop into a pregnancy and eventually a live birth.
Tony Rutherford, chair of the British Fertility Society and honorary senior lecturer at the University of Leeds, said that driving the ovaries hard with high drug doses produced more eggs but not more embryos.
"The bottom line is that the number of normal embryos is the same whether you stimulate in the conventional manner as we have for 25 years [with higher doses of hormones] or whether you do it in a much milder manner," Rutherford told The Guardian.
Stuart Lavery, consultant gynecologist and director of the IVF clinic at Hammersmith hospital in London explained that, where stimulation was not producing many eggs, "the common answer is to give more [hormonal medication]. But the work coming out suggests that isn't necessarily a good thing."
Handyside said scientists needed to look further at the pattern of abnormalities in different stimulation regimes including mild stimulation and natural cycle IVF, where one egg per cycle is removed, fertilized and returned to the woman.
"The results of such research should enable us to identify better clinical strategies to reduce the incidence of chromosome errors in older women undergoing IVF," he told the Guardian.
"We also believe that our research will help identify women who want to have their own offspring but have practically no chance of doing so that we can advise them to use donor [eggs]," said Professor Joep Geraedts, coordinator of the ESHRE task force on preimplantation genetic screening.
"This in itself is already a big step forward that will aid couples hoping for a healthy pregnancy and birth to be able to achieve one," Geraedts told The Guardian.
On the Net:
- European Society of Human Reproduction and Embryology
- London Bridge Fertility, Gynecology and Genetics Center