Medically reviewed by Dr. Shaivalini Kamarapu, MBBS, MS (Obstetrics & Gynaecology), Fellowship in Reproductive Medicine, 20+ years of clinical experience.
What is PGT?
Preimplantation genetic testing (PGT) is a test done on embryos created through IVF, before one is transferred to the womb. A few cells are taken from each embryo and tested for chromosomal or genetic problems, so that an embryo without the problem can be chosen for transfer.
PGT is not needed by every couple having IVF. It is recommended in specific situations, after discussion with your fertility specialist and, where needed, a genetic counsellor.
Types of PGT
PGT-A (aneuploidy)
Checks embryos for an abnormal number of chromosomes, a common cause of failed implantation and early miscarriage, especially as women get older.
PGT-M (monogenic)
Checks embryos for a specific single-gene condition that runs in the family, such as thalassaemia, sickle cell disease or spinal muscular atrophy.
PGT-SR (structural rearrangement)
For couples where one partner carries a balanced chromosomal rearrangement, such as a translocation, which can cause repeated miscarriages.
Who may benefit from PGT?
- Couples with recurrent miscarriages
- Couples with repeated IVF failure despite good-quality embryos
- Women of an older reproductive age, when chromosomal problems in eggs are more common
- Couples who carry, or have a child with, a known genetic condition such as thalassaemia
- Couples where one partner carries a chromosomal rearrangement
- A previous pregnancy affected by a chromosomal abnormality
How PGT works, step by step
- IVF stimulation and egg collection, usually with ICSI for fertilisation
- Embryos are grown in the laboratory to the blastocyst stage (day 5–6)
- A few cells are carefully taken from the outer layer of each embryo (the part that becomes the placenta)
- The embryos are frozen while the cells are tested in a specialised genetics laboratory
- An embryo found to be suitable is transferred in a later frozen embryo transfer cycle
Limitations of PGT
- No test is 100% accurate; prenatal testing during pregnancy is still advised
- Some embryos give unclear or 'mosaic' results that need careful counselling
- Some couples may have no suitable embryo for transfer
- PGT adds to the cost of IVF and does not guarantee a pregnancy
PGT is used only to check for medical conditions. Selecting an embryo by sex is illegal in India under the PCPNDT Act, and the sex of an embryo is never revealed or used for selection.
Frequently asked questions
The biopsy takes a few cells from the outer layer of the blastocyst, which forms the placenta, not the baby. In experienced laboratories it does not appear to reduce the embryo's chance of implanting.
No. PGT is recommended for specific situations such as recurrent miscarriage, repeated IVF failure, older maternal age or a known genetic condition in the family. Your doctor will advise whether it would help you.
Results usually take one to three weeks. The embryos stay frozen in the meantime, and a suitable embryo is transferred in a later frozen embryo transfer cycle.
Genetic screening usually tests the parents, for example to find out whether both carry thalassaemia. PGT tests the embryos created through IVF. Screening results often decide whether PGT is needed.
No. Sex selection is illegal in India under the PCPNDT Act. PGT is used only to check for chromosomal and genetic conditions.