Preimplantation Genetic Testing (PGT): Should I Test My Embryos?

Preimplantation Genetic Testing — PGT — is one of the most significant advances in IVF technology of the last two decades. It allows embryologists and geneticists to examine the genetic health of embryos before they are transferred to the uterus, enabling the selection of chromosomally normal embryos and screening for specific genetic conditions. But is PGT right for every couple? And what exactly does it involve?

This blog provides a comprehensive, evidence-based overview of PGT — what it is, how it works, who should consider it, and what its limitations are. It is written to help you have a well-informed conversation with your fertility specialist.

What is Preimplantation Genetic Testing?

PGT is a procedure performed on embryos that have reached the blastocyst stage (Day 5 or Day 6) of development. A trained embryologist performs a biopsy of 5 to 10 cells from the trophectoderm — the outer layer that will become the placenta. These cells are removed under a microscope using laser technology or micromanipulation tools. The embryo is then vitrified (frozen) while the biopsied cells are sent to a specialist genetics laboratory for analysis. Results typically take 10 to 14 days.

Crucially, the biopsy is taken from the trophectoderm — not from the ICM (inner cell mass) that develops into the baby. This minimises the potential developmental impact of the biopsy, though a very small risk remains.

Types of Preimplantation Genetic Testing

PGT-A: Testing for Chromosomal Number Abnormalities

PGT-A (formerly called PGS — Preimplantation Genetic Screening) is the most commonly used form. It screens embryos for aneuploidy — abnormal numbers of chromosomes. A normal human embryo has 46 chromosomes in 23 pairs. An aneuploid embryo may have too many or too few chromosomes in one or more pairs.

Chromosomal aneuploidy is the single most common cause of IVF failure and early miscarriage. The rate of aneuploidy in embryos increases significantly with maternal age — a key reason why IVF success rates decline from the mid-30s onward. PGT-A identifies which embryos are euploid (chromosomally normal) before transfer, dramatically improving the implantation rate per transfer and reducing miscarriage risk.

PGT-M: Testing for Single-Gene Disorders

PGT-M (Monogenic) screens for specific, known single-gene disorders in couples who are carriers. It requires preparation work with a genetic counsellor to design a unique test for the couple's specific mutation. Common conditions screened with PGT-M in India include:

•      Beta-Thalassaemia — one of the most prevalent genetic conditions in South Asian populations

•      Sickle cell anaemia

•      Spinal muscular atrophy (SMA)

•      Cystic fibrosis

•      Huntington's disease

•      BRCA1 and BRCA2 mutations (hereditary breast and ovarian cancer predisposition)

PGT-M requires that both carrier statuses are clearly established through carrier testing before the IVF cycle begins. It is a powerful tool for families with known hereditary conditions who want to prevent transmission to their children.

PGT-SR: Testing for Chromosomal Structural Rearrangements

Some individuals carry balanced chromosomal structural rearrangements — such as translocations, inversions, or insertions — that do not affect their own health but can lead to unbalanced chromosomal inheritance in offspring. Couples where one partner carries such a rearrangement often experience recurrent miscarriage or repeated IVF failure. PGT-SR screens embryos specifically for unbalanced versions of the rearrangement, identifying those suitable for transfer.

Who Should Consider PGT-A?

•      Women aged 35 and above — the risk of chromosomal aneuploidy in eggs rises significantly from this age

•      Couples with a history of two or more miscarriages — especially if these have been chromosomally tested and found to be due to aneuploidy

•      Couples who have had multiple failed embryo transfers despite good-quality embryos on morphological grading

•      Men with severe male factor infertility — associated with higher rates of chromosomal abnormality in sperm

•      Couples with a known family history of chromosomal abnormalities

•      Women over 40 using their own eggs — aneuploidy rates above 70% at this age make PGT-A particularly valuable

Who Should Consider PGT-M or PGT-SR?

•      Known carriers of Beta-Thalassaemia, sickle cell disease, or other monogenic conditions — particularly relevant in Indian populations where Thalassaemia carrier rates are high

•      Couples who have had a child with a serious genetic condition

•      Individuals with chromosomal structural rearrangements confirmed on karyotyping

•      Couples with a strong family history of hereditary cancer syndromes (BRCA1/2, Lynch syndrome)

Benefits of PGT: What the Evidence Shows

•      Higher implantation rates per transfer — transferring only euploid embryos dramatically reduces the implantation failure rate

•      Significantly reduced miscarriage rates — aneuploid embryos are the primary driver of first trimester pregnancy loss; PGT-A eliminates most of these from transfer

•      Fewer transfer cycles needed to achieve a live birth — patients who would otherwise go through 3–4 failed transfers can potentially succeed in 1–2 transfers of euploid embryos

•      Reduced risk of chromosomally abnormal live birth (e.g., Down syndrome, Edwards syndrome) — particularly valuable for women over 38

•      Peace of mind — particularly for couples with a history of recurrent miscarriage or genetic conditions in the family

Limitations and Considerations

It Does Not Guarantee Success

A euploid embryo has a significantly higher — but not guaranteed — chance of implanting. Even with PGT-A, live birth rates per transfer range from approximately 60–70% depending on the patient's age and uterine factors. Implantation is a complex biological process that involves the embryo, the endometrium, immune factors, and hormonal timing.

Mosaicism: An Evolving Area

Some embryos are found to be "mosaic" on PGT-A — meaning they contain a mix of euploid and aneuploid cells. The clinical significance and management of mosaic embryos is an active area of research. In some cases, low-level mosaic embryos can be transferred with appropriate counselling, and healthy live births have resulted. This decision requires careful discussion with your specialist and genetic counsellor.

Cost

PGT adds to the overall cost of an IVF cycle. PGT-A typically adds ₹50,000 to ₹1,50,000 depending on the number of embryos biopsied. This cost makes most clinical and financial sense in high-risk groups where multiple failed cycles or miscarriages might otherwise be the alternative.

Embryo Biopsy Risk

The biopsy procedure carries a very small risk of embryo damage when performed by trained, experienced embryologists in well-equipped laboratories. This risk is considered acceptably low in the context of the clinical benefits for appropriate candidates.

The genetic testing specialists at the Best IVF Centre in Lucknow — URvara Fertility Centre — can guide you through a comprehensive assessment of whether PGT-A, PGT-M, or PGT-SR is appropriate for your individual situation. Genetic counselling is available for all couples considering preimplantation testing.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. IVF outcomes vary based on individual health conditions. Always consult a qualified fertility specialist before making any medical decisions. The information provided here is based on current medical knowledge (2026) and should not replace professional diagnosis or treatment.