Preimplantation genetic screening (CGH)
Array CGH (aCGH) is the most well-established of the new generation of pre-implantation genetic screening (PGS) tests. It allows us to comprehensively screen embryos for abnormalities in all 24 chromosomes before transfer. Genetically normal embryos have a higher chance of implantation and the resulting pregnancies have a lower chance of miscarriage. Testing embryos by aCGH may therefore increase the likelihood of pregnancy, reduce the chances of a pregnancy loss, and improve the odds of delivery.
aCGH differs from previous PGS testing as it is able to test every chromosome, rather than a select few, so minimizes further the risk of transferring an abnormal embryo.
We have chosen to work with Reprogenetics for the genetic screening of embryos because as pioneers in the field of genetics and have been responsible for some of the most significant advances in preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS).
The Reprogenetics team has published more than 300 scientific papers concerning embryo evaluation and has received numerous awards in recognition of innovation and diagnostic service. As well as being on the cutting edge of technology, Reprogenetics also has the greatest practical experience, having performed more than 45,000 cycles of PGD in laboratories situated on four continents. The Reprogenetics laboratory in the UK is fully accredited (CPA) and provides access to the very latest methods for the genetic evaluation of sperm, eggs and embryos.
Step 1: Assisted Reproduction
Initially an IVF cycle using PGS begins in the same way as any other, with the stimulation of the ovaries to produce eggs, followed by their collection and fertilisation
Step 2: Embryo Biopsy
When the developing embryos are five days old a few cells are microsurgically removed from each by our highly trained biopsy practitioners and taken for testing (alternatively a single cell is sometimes taken when the embryos are just three days old). The cells are placed in special test-tubes and sent by courier to the Reprogenetics laboratory. The embryos under analysis do not leave the IVF clinic, they are either returned to the incubator or cryopreserved (frozen) until the test results are available.
Step 3: Genetic testing
The cells are each analysed independently by aCGH and the test results indicate how many copies there are of each chromosome, revealing any abnormal embryos. Results are available to us within 24-36 hours, although the introduction of a new ultra-rapid protocol means that we can, on occasion, have results within 4 hours. We can then choose appropriate embryos for transfer based on these genetic results as well as the standard embryological assessment of the embryos
No test is 100% accurate, so following any genetic screening we recommend that patients who become pregnant undergo prenatal testing.