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Traditionally, embryos are chosen according to their appearance under the microscope after three or five days of development in the incubator. However, in the past few years additional techniques of selection have been introduced which use high-tech methods to test embryos for genetic and chromosomal information called Preimplantation Genetic Testing for Aneuploidy (PGT-A also known as PGS). All chromosomes can be assessed and only embryos identified at low risk of chromosome abnormalities are selected for embryo transfer.

What is chromosome aneuploidy?

Chromosome aneuploidy describes the condition in which there is an incorrect number of chromosomes in an embryo. In a normal embryo there are 22 pairs of chromosomes plus two sex chromosomes. One of each pair is inherited from our mother and father in the egg and sperm in fertilisation. Most aneuploidies are lethal to the embryo and are a major cause of IVF failure and miscarriage. In rare cases, they result in abnormal pregnancy and an affected child.

The majority of aneuploid embryos (90%) occur when eggs with extra or missing chromosomes are fertilised. Sperm cells may also cause aneuploidy but the prevalence is usually lower (around 10%).

Who will benefit from PGT-A (PGS)?

All women in their late thirties and early forties should consider this option, especially if they have already had unsuccessful IVF treatment or miscarriage.

Aneuploidy screening may improve pregnancy and live birth rates, because only those embryos with normal numbers of balanced chromosomes are selected for transfer. If all embryos are found to be aneuploid, screening will enable you to make an important decision about embryo transfer and IVF treatment.

How can we detect aneuploidy?

A skilled embryologist removes one or more cells from each embryo.  The cells are sent to a laboratory to examine the number of chromosomes in the embryo using an embryo screening method known as “Next Generation Sequencing” (NGS).

Why is PGT-A red on the HFEA traffic light?

The HFEA has listed PGT-A as red on their traffic light system because there is limited evidence this treatment works well for all patients. This is why we only recommended PGT-A for women in a specific age range and on a case-by-case basis. 

For more information on the benefits, risks and the nature of clinical evidence regarding PGT-A, please read here





Meet the embryo screening team

Our dedicated team has over 25 years experience in fertility and genetics

Mr Michel Summers, Consultant in Reproductive Medicine

A graduate of King’s College, Cambridge Mr Summers completed his medical training at the University of Pennsylvania School of Medicine followed by a Clinical Fellowship in Reproductive Endocrinology and Infertility at the Brigham and Women’s Hospital, Harvard Medical School. He is certified by both the American College of Obstetrics and Gynaecology (ACOG) as well as on the GMC Specialist Register as a Consultant in Reproductive Medicine. His special interests include IVF, embryo culture, embryo implantation and preimplantation genetic diagnostics, areas of research in which he has published extensively.

Elena Linara, Senior Embryologist and Quality Lead

Elena has 10 years’ experience within embryology and is qualified in biomedical sciences, prenatal genetics and fetal medicine, and clinical embryology. She is particularly interested in ocyte and embryo vitrification, prenatal genetics, quality management, intrauterine insemination and egg sharing. Before joining the team at LWC she worked as an embryologist, andrologist and a deputy sperm bank manager.

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