Pre-implantation Genetic Screening (PGS)
PGS is a technique used to assess embryos for chromosomal abnormalities. It involves the removal of one or more cells from embryos before they are transferred. This is followed by testing of the cells to find out the number of chromosomes, using a method called array-CGH. If the cells are found to have an abnormal chromosome number, then the embryo is less likely to implant. In this way embryos can be screened in order to select the most viable embryos for embryo transfer.
What are the advantages of PGS?
- Improved success of IVF cycle: Recent research has suggested that IVF success rates might be improved if embryos are screened for chromosome abnormalities, with embryos that have the correct number of chromosomes given priority for transfer to the womb. So far, there has only been one PGS trial using the newer array-CGH method that we use, conducted in the United States. In that study, the chance of an embryo transferred to the womb making a baby was found to be increased by more than 50% in IVF cycles where embryos were chosen for transfer based upon the results of PGS analysis.
- Accurate assessment of embryos: At present the exact accuracy of array-CGH is not known, but the available data suggests that results are correct over 95% of the time.
- It can be used to diagnose Down Syndrome: Down syndrome is caused by an extra copy of a particular chromosome. In PGS the number of chromosomes is examined and likely cases of Down Syndrome can be identified.
- It can reduce miscarriage: PGS is used to identify chromosomally normal embryos. These are more likely to be healthy, and are therefore more likely to implant successfully.
PGS can be used by any person/couple undergoing an IVF cycle, but is most suitable for:
- Patients of advanced maternal age.
- Patients with repeated miscarriage.