Dr. Unnati Mamtora
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Preimplantation Genetic Testing Mumbai

What is Preimplantation Genetic Testing (PGT)?

Preimplantation Genetic Testing (PGT) is a technique performed during IVF to screen embryos for chromosomal abnormalities or specific genetic conditions before they are transferred into the uterus. It allows only chromosomally normal (euploid) embryos to be selected, significantly improving implantation rates and reducing the risk of miscarriage.

PGT is performed by a specialist embryologist who carefully biopsies 3–5 cells from the outer layer (trophectoderm) of a blastocyst-stage embryo on Day 5–6. These cells are sent to a genetic laboratory for analysis while the embryo is vitrified and stored awaiting results.

Types of Pre-Genetic Testing

PGT-A
PGT-A — Aneuploidy Screening

Screens all 24 chromosomes for numerical abnormalities (extra or missing chromosomes). Recommended for advanced maternal age, recurrent miscarriage, and repeated IVF failure.

PGT-M
PGT-M — Monogenic Disorders

Tests for a specific inherited single-gene condition (e.g. cystic fibrosis, thalassaemia, sickle cell disease, BRCA mutations). Requires preparation of a customised genetic probe before the IVF cycle.

PGT-SR
PGT-SR — Structural Rearrangements

Used when one partner carries a chromosomal structural rearrangement (translocation or inversion), to select embryos with a balanced chromosome complement for transfer.

The PGT Process: Step by Step

1
IVF Stimulation & Egg Retrieval

Standard IVF ovarian stimulation and egg collection as in a routine IVF cycle.

2
Fertilisation & Blastocyst Culture

Eggs are fertilised (IVF or ICSI) and cultured in the laboratory to the Day 5–6 blastocyst stage.

3
Trophectoderm Biopsy

3–5 cells from the outer layer of each blastocyst are carefully biopsied by the embryologist — the cells that form the placenta, not the baby.

4
Genetic Analysis

Biopsied cells are sent to the genetics laboratory. Results typically take 7–14 days. Embryos remain safely frozen during this time.

5
Frozen Embryo Transfer

Normal (euploid) embryos are transferred in a subsequent frozen embryo transfer (FET) cycle after uterine preparation.

Who Should Consider PGT?

  • Women aged 35 and above (higher risk of chromosomal abnormalities)
  • Couples with recurrent miscarriage (two or more losses)
  • Repeated IVF failure with good-quality embryos
  • Known carrier of a specific hereditary genetic condition
  • Partner with a chromosomal structural rearrangement (translocation)
  • Severe male factor infertility (associated with higher sperm DNA abnormalities)

Frequently Asked Questions

PGT significantly improves the chance of success by selecting chromosomally normal embryos, but it does not guarantee a pregnancy. Implantation also depends on uterine receptivity and other factors. It substantially reduces — but does not eliminate — miscarriage risk.

When performed by an experienced embryologist, trophectoderm biopsy on Day 5–6 is considered safe. The cells removed are destined to form the placenta — not the baby itself — and the procedure does not compromise embryo viability.

If all tested embryos are aneuploid, a fresh IVF cycle is recommended to retrieve more eggs. This is more common with advanced maternal age. Dr. Unnati will discuss all available options including egg donation if appropriate.

PGT requires embryos to be frozen while awaiting genetic results, adding approximately 4–6 weeks before the frozen embryo transfer can be performed. The embryo is not harmed by this additional freezing period.

PGT-A identifies sex chromosomes as part of the full chromosomal analysis. However, sex selection for non-medical reasons is not permitted in India under PCPNDT regulations. PGT is used strictly for medical purposes to improve pregnancy outcomes.

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