Preimplantation Genetic Testing (PGT): A Complete Patient Guide

If you are going through IVF, you will almost certainly hear about preimplantation genetic testing (PGT). This guide explains the three types, what they test, and questions to discuss before deciding whether testing fits your plan.

What PGT does

After eggs are fertilized (often with ICSI for male-factor cases), embryos are grown to the blastocyst stage (day 5–6). A few cells are gently biopsied and sent for genetic analysis. The embryo is frozen while results come back. Your team interprets the results alongside other embryo assessments.

The three types

• PGT-A (aneuploidy) — screens for the right number of chromosomes. Results describe sampled cells and can include mosaic or inconclusive findings. PGT-A does not guarantee a healthy baby or improve live-birth outcomes for every patient.
• PGT-M (monogenic) — checks for a specific single-gene condition the parents are known to carry, such as cystic fibrosis or Tay-Sachs.
• PGT-SR (structural rearrangement) — for patients with a balanced translocation or inversion, to avoid passing an unbalanced chromosome set to the embryo.

Deciding whether PGT-A fits your plan

PGT-A is not a routine requirement for every IVF patient. HFEA reports no evidence from randomized trials that it improves the chance of having a baby for most patients. It may reduce miscarriage in some circumstances, but this does not necessarily increase the overall chance of a baby. Discuss your history, available embryos, risks, costs, and alternatives with your physician.

What PGT cannot tell you

It is a screening test, not a full guarantee. It does not assess every genetic disease, and it does not grade an embryo’s developmental potential perfectly. A result reported as normal does not guarantee pregnancy or live birth. Biopsy can damage an embryo, and inaccurate or mosaic results may reduce the embryos available for transfer. Your team should explain these limitations and how results are interpreted.

Fitting PGT into your cycle

PGT adds a biopsy step and a wait for laboratory results (the embryo is vitrified in the meantime), but it does not change the stimulation itself. If you are considering it, ask how your clinic’s lab validates results and how biopsy experience compares across embryologists. To see how genetic testing sits within a full treatment plan, explore our PGT overview or speak with a physician.

Sources and further reading

• HFEA — Pre-implantation genetic testing for aneuploidy (PGT-A)