Pre-implantation genetic screening (PGS), also known as comprehensive chromosome screening or CCS, is a genetic test designed to examine embryos for chromosomal abnormalities. Embryos are biopsied at the blastocyst stage and all the chromosomes are examined.
Embryos with too many or too few chromosomes, a condition called aneuploidy, often result in unsuccessful IVF or early pregnancy loss. By only placing embryos with the correct number of chromosomes (euploid embryos) in the uterus, PGS aims to improve implantation and pregnancy rates in people having IVF.
PGS could potentially benefit many people who are planning to do IVF, specifically those of advanced reproductive age or those with a history of recurrent pregnancy loss.
PGS may help to:
• Reduce the chance of having a miscarriage
• Reduce the risk of an abnormal pregnancy
• Reduce the time and cost to achieve a healthy baby by helping choose the best embryo(s) to transfer
• Reduce the risks associated with the transfer of multiple embryos at a time
How does PGS work?
PGS is used in conjunction with in vitro fertilization (IVF) and uses the most sophisticated and scientifically validated technology. PGS examines all 24 chromosomes, the 22 non-sex chromosomes, plus the two sex chromosomes (X & Y) for any gains or losses, otherwise known as aneuploidy.
Only embryos with the correct chromosome complement will be transferred. Sometimes PGS detects what is known as mosaicism which describes a situation in which different cells in the same embryo have different numbers or arrangements of chromosomes. When people only have mosaic embryos available for transfer, genetic counselling is advised prior to embryo transfer.
Regardless, all patients who are interested in PGS will meet with a Genetic Counsellor to ensure they are fully informed before moving forward with an IVF-PGS cycle.
What is the process for PGS?
In terms of the cycle itself, the entire procedure consists of five different steps, usually performed by different experts and laboratories:
The entire procedure consists of five different steps, usually performed by different experts and laboratories:
• Patients having PGS undergo ovarian stimulation and IVF-ICSI to create embryos.
• The second part involves embryo biopsy performed by an embryologist. The biopsy, which takes place at the appropriate stage for the ordered testing, is done to remove material from the embryo.
• The biopsy samples are then transported to the appropriate genetics reference laboratory.
• The genetics reference laboratory analyses the biopsy samples. The result comes in around two weeks.
• Should there be embryos for transfer, this will take place in our clinic no sooner than the next month after the IVF cycle. Usually, the embryos are frozen after biopsy. A frozen, thawed embryo transfer is planned in the next month if genetic testing demonstrates at least one unaffected and/or chromosomally normal (euploid) embryo for transfer.
What is Gender Selection?
Gender selection, or sex selection, is a fertility procedure used to choose the gender of a baby prior to conception. While the desire to choose a baby boy or a baby girl has probably been present throughout human history, it is only recently that the technology to do so has become clinically possible and available. With improvements in gender selection technology, the demand for gender selection has also been growing steadily.
Preimplantation Genetic Diagnosis (PGD) is an advanced genetics test used with in vitro fertilization to determine the status of an embryo’s chromosomes. PGD prenatal diagnosis is performed on early embryos prior to implantation in the uterus and initiation of pregnancy.
The PGD is being done before the embryo’s genetic materials become “active”. Because PGD is done at the stage where the cells are completely identical and each cell has the potential of being any part of the infant, any cell biopsy at this stage is deemed safe. Therefore, the PGD procedure is completely safe and defect-free.