New technology could help IVF success rate
Published Mar 31, 2009
Thirteen failed IVF cycles is just too many. Yet many women continue treatment hoping to achieve a viable pregnancy. Using new technology known as Array Comparative Genomic Hybridization (Array CGH) researchers at Care Fertility in Nottingham, enabled a 41-year-old woman to conceive after 13 failed cycles of IVF treatment. She is due to give birth in two months time.
IVF success rates have gradually increased since this procedure was first introduced in 1978. Improved success was due to both procedural advances as well improved patient screening that allowed identification of those patients with the greatest chance to achieve a pregnancy.
However, improved pregnancy rates are only half the story along with increased success has come a dramatic increases in the risk of multiple pregnancy. Clinicians are faced with the dilemma of patients demanding the highest pregnancy rates hand in without concern for the risk of high order multiple births. In many countries, guidelines restrict the number of embryos transferred. As a result, pregnancy rates may be reduced. CGH may offer an option that solves this dilemma.
IVF success defined as deliveries per started cycle are reported at 25-45% with most of the variation due to the patient age and selection process. When embryos are evaluated by removing a single cell and testing a few chromosome pairs to see if the embryo has the normal two copies for each chromosome around 85% of the embryos come up abnormal in this very limited evaluation. That explains why when the embryologist simply looks at the embryo to determine which embryo might be best to transfer, they are often wrong. Even the perfect appearing Day 5 blastocyst may contain genetic errors.
Recent studies have demonstrated that preimplantation genetic screening (PGS) may not result in an overall improvement in the delivery rate. So, researchers have been looking for screening methods that offer greater ability to determine the implantation potential for a single embryo. Early data suggests that CGH may be what we have been looking for. By removing 8-10 cells from a blastocyst embryo on the fifth day after retrieval and testing those cells per embryo implantation rates of up to 66% have been reported.
As CGH takes about a week or two to get results, the embryos must be cryopreserved and transferred in a subsequent treatment cycle. And, there is not yet a clear answer whether removing the cells and freezing the embryos will ultimately adversely affect the embryo. We await the opportunity to review more data to learn whether CGH alone or in combination with other techniques may at some time in the future allow us to transfer a single embryo with a high level of confidence that a pregnancy will result.