Preimplantation Genetic Screening, or PGS, is a genetic test which allows doctors to screen IVF embryos for abnormalities in chromosome number. Using genetically normal embryos improves the chances of successful implantation and decreases the risk of miscarriage. Thus, PGS testing may also improve your chances of successful IVF treatment.
How is PGS performed?
Prior to PGS, the standard IVF procedure will be carried out. The egg is fertilised by the sperm and the embryos are allowed to divide for up to five days, into multiple cells.
The resulting embryos will then be screened using PGS in the following way:
- One or more cells will be removed from the embryos, after which the embryos will be frozen.
- The cell’s DNA will then be analysed to determine the number of chromosomes present.
- Fertility doctors will then select the embryos of the highest quality for transfer into the uterus. Any good quality embryos that are left over can be frozen for future use.
Do I need PGS testing with IVF?
PGS is advised for couples or individuals who may be at risk of abnormal embryos. You may be offered PGS if you meet any of these criteria:
- You have a history of genetic problems, which may be passed on to the offspring (PGD procedure will be useful in this case)
- You have had several failed fertility treatments
- You have experienced recurrent miscarriages, including ‘chemical’ pregnancies
- You are seeking IVF after the age of 35
Will PGS improve my IVF results?
PGS has been shown in numerous studies and in clinical data to improve the success rates of IVF. The benefits of including PGS testing within your IVF cycle include:
- Higher chance of successful implantation
By only transferring healthy embryos into the uterus, fertility doctors can improve the chances of a successful clinical pregnancy
- A reduced risk of miscarriage
Recurrent miscarriages may be caused by chromosomal abnormalities in the embryo. Therefore, choosing healthy embryos with PGS also reduces the risk of miscarriage.
- Speed up successful IVF process
PGS can reduce the amount of IVF cycles required to achieve a successful pregnancy. Thus, reducing the amount of time needed to become pregnant and the financial costs of additional cycles.
- Remove risk of multiple pregnancies
By transferring only one, healthy embryo, doctors can remove the risks of multiple pregnancies in IVF
- Can increase the chances of having a healthy baby
Some chromosomal abnormalities can also lead to babies being born with serious illnesses. PGS minimizes such risks.
How much does PGS cost?
Additional costs are associated with PGS testing as this is a specialist laboratory procedure. The pricing is based on the number of embryos to be analysed. The average costs of PGS for up to five embryos are given below:
IVF with PGS in the USA – starts from around $20,000
IVF with PGS in Thailand – starts from around $12,500
IVF with PGS in Malaysia – starts from around $12,000
IVF with PGS in India – starts from around $8,000
IVF with PGS in the UK – starts from around £9,000
IVF with PGS in Spain – starts from around €8,000
Is PGS testing safe?
As this procedure involves removing a sample of cells, you may question whether it can cause any lasting damage to the embryo.
Fertility doctors have vast experience of performing this procedure successfully over many years. When carried out by a highly experienced doctor, the risks of this procedure are minimal. This is corroborated by a study published in Human Reproduction in 2010, which demonstrated that the embryo biopsy involved in PGS testing does not increase the risk of birth defects at all.
Risks and limitations of PGS
It is important to discuss the risks and limitations of such procedures. These include the following:
- As discussed above, given that PGS is an invasive procedure, there is a slight risk of damage to the embryo during the removal of cells, if not performed by an experienced doctor
- No suitable embryos may be found during the procedure. This can often be an issue in cases of advanced maternal age, where abnormalities become more common.
- It is possible that inconclusive results may be obtained, in a phenomenon known as mosaicism. This occurs when embryos contain both normal and abnormal cells.
How long does PGS take?
If you would like PGS testing alongside IVF, you will need to allow an additional 7-10 days for the embryos to be screened prior to implantation.
PGS can be performed on fresh embryos at day 3 of development, then they may be implanted on day 5. However, in order to get the best results and minimise the risks, it is recommended to perform PGS only on day 5 embryos.
Alternatives to PGS testing
Another option for genetic testing prior to implantation of an embryo is PGD, or Preimplantation Genetic Diagnosis. This is a much more specific test, which looks to identify the presence of gene mutations which are linked to certain genetic disorders. PGD may be recommended if you or your partner is carrier for specific genetic disorders.
Alternatively, you may consider prenatal screening options, which will be performed after the pregnancy has been confirmed. These include:
- Chorionic Villus Sampling (CVS)
This involves a small sample of cells being taken from the placenta, between weeks 10-12 of the pregnancy. These samples are analyzed for chromosomal or genetic disorders in the fetus.
- Amniocentesis
This involves a small sample of cells being taken from the amniotic fluid, between weeks 16-18 of the pregnancy. These samples are also analyzed for chromosomal or genetic disorders in the fetus.
- Ultrasound and blood tests
These may provide additional information regarding potential genetic problems during the pregnancy.
Noting the benefits of PGS testing, many fertility doctors offer it as a routine procedure to improve success rates for IVF patients. They reports success rates of 65-80%, which are much higher than the average of 40-50% reported in regular IVF cycles.