Several newspapers report today on a “dramatic IVF breakthrough” that screens embryos for genetic defects and greatly increases the chance of a woman becoming pregnant.
The Guardian reports that an Oxford-based team of doctors conducted a trial that found that selecting embryos with the new technique “improves the chances of them implanting in the mother’s womb by nearly 2.5 times”. The full results will be announced later this week at a conference.
The news reports are based on a study of a technique called comparative genomic hybridisation (CGH), used when screening embryos for IVF.
The study has not been published in full yet. The research will be presented at the American Society of Reproductive Medicine's (ASRM) annual conference in Atlanta this week.
According to a press release, the researchers enrolled 115 patients from the Colorado Centre for Reproductive Medicine in the US. Cells from these patients’ embryos were transported to Oxford for CGH analysis, where more than 500 embryos were tested.
The study found that 66% of women became pregnant after screening, which was twice as many women who fell pregnant without it (28%). Many of the women in this study were aged 39 and most had failed two cycles of IVF.
The lead researcher, Dagan Wells, is a senior fellow at Oxford and Director of Reprogenetics UK, a company supplying pre-implantation genetic diagnostic services. He is quoted as saying that the study is biased towards success. This is because most women had more than one embryo transferred (therefore increasing the chances of implantation), and also had blastocysts transferred (embryos at a later stage of development).
However, he also said that “if we transfer one embryo, we would expect two-thirds of women to get pregnant”.
The research has not been published and no conference abstract was available to review so it is not possible to comment in depth on the quality of this study. It appears that there was a control group, but the research is not being described as a randomised controlled trial, which would provide the most robust evidence of effect.
The lead researcher is quoted in the press release as saying, “if the results are replicated - particularly in a randomised controlled trial - then I think there would be an argument for making this the standard of care”. More detail will be available after the presentation of this research at the ASRM conference this week.
CGH is a form of pre-implantation genetic screening (PGS) used to detect abnormalities in the number of chromosomes in an egg or embryo.
It is an assistive reproductive technology, which screens embryos for genetic abnormalities to increase the chances that only those free of genetic diseases are used, in this case, embryos free of ‘aneuploidy’ or too many chromosomes.
Women are required to undergo in-vitro fertilisation (IVF) so embryos can be taken for evaluation. Usually PGS tests cells from three-day-old embryos grown in the laboratory. Only embryos with the normal number of chromosomes are then transferred back to the mother.
CGH was performed on blastocyst embryos (five-day-old embryos) as opposed to three-day-old embryos. Five-day-old embryos consist of two different types of cells, and IVF using embryos at this stage of development is usually more effective than using less developed embryos. More cells can be taken from the embryo for testing, and the technique also allows all 23 chromosome pairs to be examined.
This gives it an advantage over other PGS techniques which only examine up to 12 pairs of chromosomes. CGH compares a sample of the blastocyst’s DNA with a normal control sample and detects abnormal chromosomes using fluorescent dyes. The press release about this study reports that CGH can also be performed on three-day-old embryos.
The Human Fertilisation and Embryo Authority, an independent regulator overseeing the use of embryos in fertility treatment and research, reports that currently CGH is only offered by a couple of clinics, but that clinics regularly apply to add new PGS techniques to their licence. They provide a search facility on their website that allows users to search for a clinic that offers PGS (and CGH).