Preimplantation Genetic Testing for Aneuploidy (PGT-A), previously known as Preimplantation Genetic Screening (PGS), is a method of examining an embryo to determine the number of chromosomes in the embryo’s cells. This is performed in the laboratory before the embryo has a chance to cause a pregnancy.
Every healthy human being has 46 (23 pairs) of chromosomes, when the cells of an embryo have this complete set of chromosomes, it is referred to as euploid. When the cells of an embryo have an abnormal number of chromosomes it is known as aneuploid. Most aneuploidies are incompatible with life and as such, after having been transferred to the uterus, they do not implant, or even if they do implant, they result in failed pregnancies.
There is, however, a small fraction of aneuploidies compatible with life, such as Down syndrome, for instance, which is caused by the presence of an extra chromosome number 21. In other words, in such cases, a human being has 47 chromosomes, instead of 46.
Aneuploidies compatible with life:
Trisomy 21: Down syndrome
Trisomy 18: Edwards syndrome
Trisomy 13: Patau syndrome
Sex chromosome aneuploidies, such as 47 XXY Klinefelter syndrome in men
45 XO Turner syndrome
47 XXX triple X syndrome
47 XYY Jacobs syndrome.
With age, the risk of aneuploidies in women increases drastically. Our clinic’s statistics reveal that while about 45% of the embryos are aneuploid in women aged 28-35, the incidence is as high as 85% in women aged 39-45. Preimplantation Genetic Testing for Aneuploidy (PGT-A) not only enables us to identify embryos compatible with life, but also allows us to save women emotional stress and protect their health from miscarriage-related complications.
PGT-A is prescribed in the following cases:
Advanced maternity age (over 35)
Several failed pregnancies
Unsuccessful treatment with In Vitro Fertilization
Chromosome aneuploidy of the fetus during previous pregnancy
Disorders caused by structural abnormalities in chromosomes as found in the medical history of the family
Disorders caused by a mutation in individual genes as found in the medical history of the family (monogenic disorders): autosomal recessive, autosomal dominant and X-linked disorders—for example, cystic fibrosis, hemophilia, thalassemia, and Duchenne muscular dystrophy. In many cases genetic testing of the partners reveals that they are carriers for genetic disorders not revealed in their family history.
PGT-A consists of the following stages:
When a patient receives In-Vitro Fertilization (IVF) at ReproART, the embryo’s development up to a certain stage proceeds outside the body, in the IVF Laboratory. That is when the embryo’s biopsy is performed.
On the third day of the embryo’s development, assisted laser hatching is performed on a small section of the outermost layer that surrounds but is not part of the embryo. On day five or six, when the embryo reaches the blastocyst stage, trophectoderm biopsy is performed, removing a few cells that extend through the hole in the outermost layer. The trophectoderm is a constituent part of the blastocyst, which subsequently becomes the placenta. Subsequently, the biopsied cells are sent for genetic testing to our partners, leading laboratories in Great Britain or United States of America, with whom we maintain active cooperation.
Although cells that would have become placenta are removed the cells that will become the fetus and the baby are not harmed. Following biopsy embryos are cryopreserved until genetic test results are reported. Upon thawing embryos recover and develop normally.
PGT-A Success Rates at ReproART
Most embryonic aneuploidies are incompatible with life. Even if they implant in the uterus, they fail to develop and result in miscarriage. Preimplantation Genetic Testing for Aneuploidy (PGT-A) is designed to calculate the number of chromosomes in each embryo and to identify euploid (healthy) embryos.
Following PGT-A, the obstetrician/gynecologist/fertility doctor transfers an embryo with the required number of chromosomes (46) into the patient’s uterus. Transferring a euploid (healthy) embryo identified through chromosome testing drastically increases pregnancy chances.
In particular, PGT-A triples pregnancy chances in women aged 40+, and reduces the incidence of miscarriages after conception to one-third of the rate with untested embryos.
The pregnancy chances of a woman aged 40 are 10-14%, and the miscarriage risk is 50%, during treatment at the ReproART Fertility Center. However, in the case of PGT-A, and the transfer of a euploid embryo, pregnancy chances increase to 50%, and miscarriage risks drop to 10%.
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To plan consultations with ReproART Fertility Specialist, please set an appointment in advance or request more information.