Preimplantation Genetic Testing: PGT-A, PGT-M and PGT-SR
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What is Preimplantation Genetic Testing?
Preimplantation Genetic Testing (PGT) is a test performed on a small sample of cells taken from the embryo to screen for chromosomal variations and specific known genetic conditions. Chromosomes are structures made of protein and DNA that carry genetic information to instruct our body to grow, develop and function.
Types of PGT
There are three types of PGT tests available through Thrive Fertility:
Preimplantation Genetic Testing for Aneuploidy (PGT-A)
A chromosomally normal, or euploid embryo, contains 23 pairs of chromosomes (46 in total). One set of chromosomes comes from the egg and the other from the sperm. Euploid embryos suitable for embryo transfer have a higher rate of successfully implanting and creating a healthy, ongoing pregnancy compared to untested embryos.
Preimplantation Genetic Testing for Monogenic (Single Gene) Disorders (PGT-M)
PGT-M allows you to reduce the risk of passing on a known genetic variant to your child. This includes conditions such as cystic fibrosis, thalassemia, Huntington’s disease and BRCA-1/2 mutations. Additional testing for yourself, your partner and family may be required prior to PGT-M testing.
Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR)
With chromosomal translocation the correct number of chromosomes are present, but the structure is rearranged. Balanced translocation may be picked up in a karyotype test prior to starting IVF. People with balanced translocations may have a higher risk of recurrent miscarriage. Only chromosomally balanced embryos will be transferred.
Preimplantation Genetic Testing for Aneuploidy (PGT-A)
A chromosomally normal, or euploid embryo, contains 23 pairs of chromosomes (46 in total). One set of chromosomes comes from the egg and the other from the sperm. Euploid embryos suitable for embryo transfer have a higher rate of successfully implanting and creating a healthy, ongoing pregnancy compared to untested embryos.
Preimplantation Genetic Testing for Monogenic (Single Gene) Disorders (PGT-M)
PGT-M allows you to reduce the risk of passing on a known genetic variant to your child. This includes conditions such as cystic fibrosis, thalassemia, Huntington’s disease and BRCA-1/2 mutations. Additional testing for yourself, your partner and family may be required prior to PGT-M testing.
Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR)
With chromosomal translocation the correct number of chromosomes are present, but the structure is rearranged. Balanced translocation may be picked up in a karyotype test prior to starting IVF. People with balanced translocations may have a higher risk of recurrent miscarriage. Only chromosomally balanced embryos will be transferred.
Preimplantation Genetic Testing for Sex Selection
With chromosomal translocation the correct number of chromosomes are present, but the structure is rearranged. Balanced translocation may be picked up in a karyotype test prior to starting IVF. People with balanced translocations may have a higher risk of recurrent miscarriage. Only chromosomally balanced embryos will be transferred.
How does the PGT process work?
When undergoing PGT, the process may look something like this:
Who is PGT suitable for?
Your fertility specialist may recommend PGT testing for:
- Advanced maternal age.
- History of recurrent implantation failure or miscarriage.
- History of pregnancy with a chromosomal variation.
- Known single gene mutations (such as cystic fibrosis or BRCA gene mutation) to avoid passing the condition to future children – PGT-M.
- Translocation – either you or your partner has a chromosomal rearrangement that can lead to miscarriage or health issues in the affected child – PGT-SR.
Risks and limitations of PGT
PGT is a screening tool and does not guarantee 100% accuracy. We still recommend NIPT (non-invasive prenatal testing) for a pregnancy achieved with a euploid embryo.
- There is a small risk of damage to the embryo during the biopsy process and in rare cases loss of the embryo.
- Not all embryos will be suitable for PGT testing.
- Embryos may come back with ‘no result’ or ‘inconclusive result’. Some results will require further genetic counselling to assist informed decision-making.
- Embryos with an abnormal result will not be suitable for transfer.
- PGT does not improve cumulative success rates, however, it may reduce the time to pregnancy by selecting only chromosomally normal embryos for transfer.
Thrive Fertility was born from our personal experience of infertility. We’ve been where you are, we know what it’s like. That’s why we provide a range of support services throughout your IVF journey.
PGT FAQs
PGT-A screens embryos for chromosome count issues (aneuploidy). PGT-M tests for a known single-gene condition in the family. PGT-SR assesses for structural rearrangements such as translocations or inversions. These tests inform embryo selection but do not guarantee a pregnancy.
Results are typically returned to your doctor within about 2–4 weeks of embryo biopsy. Timeframes may vary by laboratory workflow.
Sex selection for non-medical reasons is not permitted. In limited circumstances, sex determination may be involved where medically indicated and appropriately approved. For individual guidance, please speak with your treating specialist.
How can we help?
At Thrive Fertility we want to support you on your journey to parenthood. We believe that IVF should be accessible and want you and your family to flourish.
We can explore the reasons you may be struggling to conceive and advise you on the options available to you, which may include IVF.