# PGT-A

> Citation bundle for PGT-A on The Treatment Registry.
> URL: https://thetreatmentregistry.com/procedures/pgt-a
> Bundle URL: https://thetreatmentregistry.com/api/citations/procedures/pgt-a

- Category: ivf-fertility

## Description

Preimplantation genetic diagnosis is the genetic profiling of embryos prior to implantation, and sometimes even of oocytes prior to fertilization. PGD is considered in a similar fashion to prenatal diagnosis.

## Overview

PGT-A (preimplantation genetic testing for aneuploidy) is a genetic test performed on embryos created through in-vitro fertilisation to check whether they have a normal number of chromosomes. It is a form of preimplantation genetic screening, testing embryos obtained through IVF or ICSI for aneuploidy, an abnormal number of chromosomes, and it was formally renamed preimplantation genetic diagnosis for aneuploidy (PGD-A) by the Preimplantation Genetic Diagnosis International Society in 2016. Because it requires embryos to examine, PGT-A is an adjunct to assisted reproductive technology and depends on IVF to obtain the eggs or embryos. A small sample of cells is taken by biopsy, generally at the blastocyst stage around day 5 or 6 of development, which has proved less harmful to the embryo than earlier blastomere (cleavage-stage) biopsy. The DNA from the sampled cells is then analysed for chromosome number, so that embryos with the expected chromosome complement can be identified for transfer to the uterus. By screening for aneuploidy, the aim is to help identify embryos with a better chance of a successful pregnancy. The technique is distinct from testing for single-gene (monogenic) diseases: rather than looking for a specific inherited mutation, PGT-A assesses the overall count of chromosomes. It is an invasive procedure that requires serious consideration, and its usefulness can depend on factors such as the woman's age and the stage of development at which the biopsy is performed.

## Common risks

- Damage to the embryo during the biopsy, which can destroy the embryo
- Loss of embryos during freezing and thawing (about 20% of thawed embryos do not survive)
- Lower live-birth rate reported with cleavage-stage biopsy in women of advanced maternal age
- Increased perinatal death rate reported in multiple (twin or higher-order) pregnancies

## FAQs

### What is PGT-A?

PGT-A is preimplantation genetic testing for aneuploidy. It screens embryos created through IVF to check whether they have a normal number of chromosomes, so that embryos with the expected chromosome complement can be selected for transfer.

### How is PGT-A different from PGT-M?

PGT-A checks the number of chromosomes in an embryo (aneuploidy screening), whereas PGT-M tests for a specific single-gene, or monogenic, disorder. PGT-A counts chromosomes rather than looking for a particular inherited mutation.

### Does PGT-A require IVF?

Yes. Because embryos are needed for testing, PGT-A is an adjunct to assisted reproductive technology and requires in-vitro fertilisation to obtain the oocytes or embryos to be evaluated.

### When and how is the biopsy done?

A small sample of cells is taken by biopsy, generally at the blastocyst stage around day 5 or 6 of development. This blastocyst biopsy has proved less harmful to the embryo than earlier cleavage-stage biopsy.

### Why is PGT-A performed?

It is used to screen embryos for an abnormal number of chromosomes, with the aim of identifying embryos that have a better chance of leading to a successful pregnancy.

### What are the risks to the embryo?

The biopsy is invasive and can damage or destroy the embryo. There is also loss during freezing and thawing, with about 20% of thawed embryos not surviving, and some studies report poorer outcomes with cleavage-stage biopsy in older women and in multiple pregnancies.