Why Should I Consider PGT-A in my IVF Treatment?

Karen Sage is the UK's first Genetic Counsellor specialising in fertility and she leads the Genetic Service at CARE Fertility. 


Why should I consider PGT-A in my IVF treatment?

PGT-A, previously known as preimplantation genetic screening (PGS), is the process of testing an embryo for genetic problems during the course of an IVF cycle. Why do we do this, what are the benefits and why should you consider this in your IVF treatment?

Why consider PGT-A?

A woman’s fertility and her ability to conceive a healthy pregnancy naturally decreases with age.  The natural decline in female fertility starts in the mid-30s and progressively decreases every year as the quantity & quality of the eggs remaining within the ovaries decline.

The reduction in the quality of the eggs is caused by a deterioration of the biological functions which control the duplication and division of their genetic information.   The frequency of these errors increases with the age of the eggs, giving rise to the number of genetic anomalies which develop and subsequently reduce the chance of successful pregnancy.  This is believed to be the main reason why older women have greater difficulty getting pregnant, are more likely to miscarry and are at risk of have a pregnancy affected with a chromosomal abnormality.

Male fertility also starts to decline around age 40 to 45 years, as testicular function and sperm parameters deteriorate.  Furthermore, age-associated genetic disorders increase, which contribute to an increasing rate of chromosomal abnormalities in embryos created from older men.


Is PGT-A suitable for me?

PGT-A can be applied to the treatment of anyone undergoing an IVF cycle.  A recent randomised controlled trial (RCT), the STAR trial, established that PGT-A was most clinically significant for woman aged >35 years.

Regardless of age however, PGT-A is often recommended to patients who have suffered recurrent cycles of IVF failure or multiple unexplained pregnancy loss or miscarriage.  Furthermore, PGT-A is recommended for the treatment of those whereby the man is older (>40 years) and has a higher risk of having sperm with genetic abnormalities.


PGT-A process and benefits

PGT-A requires that a relatively small number of cells are removed from the embryo at the blastocyst stage during the course of an IVF treatment.  These cells can then be screened using genetic tests which can establish if the embryo is either healthy and has the correct numbers chromosomes, or contain abnormalities, which may lead to failed implantation, miscarriage or a birth anomaly. 

Following PGT-A, the embryos which have been identified as being free from any chromosomal abnormality can then be selected and returned back to the body for a pregnancy to establish itself.

What must I also be aware of?

Some more recent research has shown that sometimes not all the cells in an embryo are identical, therefore the genetic testing of a few cells may not be representative of the whole embryo.  This unusual biological occurrence, estimated to occur is ~5% of cases, is known as mosaicism.

PGT-A has evolved as a technology which relies on the small number of cells tested as being representative of the embryo as a whole.  However, the presence of mosaicism does mean that it is possible for an embryo to be diagnosed as being healthy when in fact it could still contain an abnormal.  Research is currently in motion to improve our understanding of mosaicism.


What are the successes of IVF treatment with PGT-A?

The following pregnancy successes were achieved at CARE London for Jan – Dec 2018:

PGT-A treatments (Average Age : 37 years)

Positive Pregnancy Tests


73 %

Clinical Pregnancy


55 %

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