Preimplantation Genetic Screening (PGS) is a form of IVF genetic testing that checks if your embryos have the right numbers of chromosomes for a successful ongoing pregnancy, at an early stage prior to embryo transfer.
Some embryos which may appear normal under the microscope may in fact be chromosomally abnormal – known as aneuploidy - and don’t have the required 46 chromosomes in each cell.
As the embryo’s genetic ‘instructions’ are incorrect, it can’t form a healthy baby, and in many cases affected embryos either do not implant or miscarry.
PGS may be discussed with you as part of your IVF cycle if you have:
- Had recurrent pregnancy loss/miscarriage
- A history of failed IVF despite the transfer of what appear to be good quality embryos
- Are an older woman. Older women are at a higher risk of producing abnormal embryos due to age.
Benefits of Preimplantation Genetic Screening
Preimplantation Genetic Screening may:
- Help you achieve pregnancy in the least number of IVF cycles.
- Help you avoid future failed IVF cycles and pregnancies. If PGS shows you have only abnormal embryos, you can consider alternative ways to have a family such as the use of donor sperm and donor eggs.
- Significantly reduce the risk of pregnancy with an abnormal embryo, which is likely to reduce your risk of miscarriage.
- Detect the majority of affected embryos before IVF transfer, improving your chance of a healthy pregnancy.
Meet our first PGS baby
Joanne and Andrew had their baby, Ernest Thomas, with the help of PGS.
Baby Ernest was born in April 2018, after our fertility doctors identified that genetically-abnormal embryos together with a misplaced window of implantation were the cause of the couple’s fertility struggles.
You will undergo ovarian stimulation to produce mature eggs, which are then fertilised in our laboratory. We will monitor embryo development.
We will advise if any of your embryos reach the required Day 5 Blastocyst stage for PGS testing. We will check your embryos have high-quality cells and are suitable for biopsy.
Several cells will be carefully taken from each embryo by our embryo biopsy practitioners and transferred to a special genetics laboratory for testing.
Whilst we await your PGS results, your embryos are cryopreserved. Results take around two weeks.
Our embryologists will use the results to determine which of your embryos are suitable for transfer. By using PGS, it is very likely that you will have fewer embryos available for transfer than you would have had if you did not do PGS. This is because embryos that test grossly abnormal are not transferred.
Frozen Embryo Transfer
You will undergo a Frozen Embryo Transfer, which involves optimising and preparing your uterus for pregnancy and precisely timing your embryo transfer. Only one embryo will be thawed and transferred in each cycle to reduce your risk of multiple pregnancy.
Should I have PGS as part of my IVF cycle?
Deciding to proceed with PGS is a very sensitive and individual decision.
Your Manchester Fertility consultant will discuss the benefits and risks with you in your particular case, so you can make an informed choice about whether to have PGS in your IVF treatment.
PGS identifies if an embryo has more or less whole chromosomes than the required number to develop into a healthy baby – so it may not detect abnormalities involving smaller pieces of chromosomes and other types of chromosome anomalies.
PGS, genetics and gender
PGS does not detect genetic disease mutations or test for specific genetic conditions. We cannot tell you the gender of an embryo.
PGS suitable embryos
PGS can only be performed on embryos that have reached Day 5 Blastocyst stage. This is because PGS tests the cells from the embryo that form the placenta. Only embryos that have reached Blastocyst stage will have these cells.
PGS is a very delicate and intricate procedure using state of the art technology, and Manchester Fertility embryologists have had intensive embryo biopsy training to perform PGS, with less than 1% risk of damage to an embryo during cell extraction.
PGS and frozen embryos
PGS can be performed on embryos already frozen in storage with us. We can thaw these to perform testing if advised. Your embryos will need to be re-frozen afterwards, which we can do successfully and at minimal risk to your embryos.
PGS may show you have no normal embryos which are suitable for transfer. And although PGS is highly accurate, the risk of a pregnancy affected by a chromosome abnormality is not removed entirely.
Learn more about the testing we can carry out, fertility treatments and how we can help you have a baby in our Learning Centre. Read through our blog library, browse our FAQs, explore our patient guides or ask us a question via our free Ask the Expert tool.
"Thank you so much to everyone at Manchester Fertility who has helped us create our gorgeous family"