PGT-M and PGT-A
As the first clinic in Europe, we began to perform pre-implantation genetic diagnosis and screening on 5 to 6-day-old embryos – blastocysts thanks to our cooperation with Australian Genea World Leading Fertility. Currently, we provide all the possible PGT-M and PGT-A (former PGD and PGS) testing using NGS and PCR methods. PGT-M and PGT-A increase your chances of getting pregnant by more than 30 %.
PGT-A is basically the search for any change in the genetic makeup of an embryo. Using PGT-A methods, we control the entire DNA in large sections at the level of chromosomes or parts thereof. In our laboratory, the NGS technique is used for PGS.
The NGS technique is more accurate and provides more information about the chromosome status of individual embryos. The NGS technique is more accurate and provides more information about the chromosome status of individual embryos. The method works on the principle of parallel sequencing, ie the sequences of thousands to millions of fragments are determined simultaneously.
Compared to the previously used aCGH method, next generation sequencing has a higher resolution. This fact makes it possible to detect some mosaicist embryos, which were evaluated as healthy, which could theoretically lead to a reduction in the success of implantation. A higher probability of detecting a change in the structure and number of chromosome parts (≥10 Mbp) and thus detecting inappropriate embryos in parents with a balanced translocation was also described.
Thanks to this technique, we can detect numerical chromosome aberrations, most often leading to miscarriage in the early stages of pregnancy or to the birth of a child with a severe disability. The best known syndrome is Down syndrome, caused by supernumerary chromosome 21.
PGT-M is about finding a specific genetic change – a mutation. PGT-M methods are also intended for parents who carry a balanced form of translocation, ie the rearrangement of genetic material between chromosomes. It is PGT-M that can offer them the choice of an embryo that does not carry an unbalanced form of translocation, ie a form associated with multiple fetal losses or the birth of an affected offspring.
Thus, by using the NGS method for PGT-M / PGT-A, it is possible to increase the success of assisted reproduction and reduce the risk of congenital malformations.
Why is it desirable to carry out genetic testing?
The vast majority of reproductive losses (about 80 %) or the mere non-attachment of the embryo in the uterus can be caused by so-called chromosomal aberrations, ie pathological changes in the DNA of the embryos. These can be caused by poor division of embryo cells for various reasons.
The number of chromosomal aberrations in germ cells has also been shown to increase with maternal age. PGS methods are a great help in selecting an embryo without these chromosomal aberrations, increasing the likelihood of its attachment and proper development in the uterus. PGD methods for alteration make it possible to exclude embryos carrying a particular serious disease (in the case of monogenic diseases) or to exclude embryos carrying unbalanced changes in DNA (in the case of translocations).
A big benefit of PGT-M / PGT-A is also financial savings. At our clinic, we use extended cultivation, when only the highest quality embryos grow by the 5th or 6th day.
Embryo transfers with chromosomal aberrations associated with spontaneous abortions are then minimized. Reducing the psychological burden, which is often associated with assisted reproduction, also plays an important role.
Am I sure that I will have a healthy child using PGT-M / PGT-A?
The benefit of PGT-M / PGT-A techniques lies mainly in embryo selection and in increasing the likelihood of pregnancy. In one woman’s menstrual cycle, this probability is around 25 % depending on the woman’s age. Thanks to the techniques used in PGT-M / PGT-A, the probability of pregnancy increases in our workplace to almost 75% during the transfer of one embryo. In the case of PGT-A, an embryo without changes in the number of chromosomes is selected, and women are then spared unnecessary embryo transfers and subsequent reproductive losses due to the absence or excess of chromosomes in the embryo.
In the case of PGT-M, there is up to a 99% probability that the embryo does not carry the specific disease for which it was examined or does not carry an unbalanced translocation. However, there is, of course, the possibility that events that affect the genome will occur during intrauterine development. Whether it is various infections or physical causes. There is always a risk of giving birth to a child with one of the developmental defects. These congenital malformations also include less serious defects such as mild cleft palate defects, etc.
In any case, great attention should be paid to the prenatal screening program of the attending gynecologist. Thanks to a well-developed system of prenatal care in our country, the risk of giving birth to a genetically affected offspring is reduced to a minimum.
How is PGT-M / PGT-A performed?
PGT-M / PGT-A is bound to artificial insemination (IVF).
After collection of eggs, their fertilization and 5-6 days of cultivation, a biopsy is performed on suitable embryos (several cells are collected).
These de-biopsied cells are subsequently tested (NGS, PCR) by a pre-selected technique. All quality embryos are frozen (vitrified) after biopsy and the transfer then takes place in one of the next cycles.
PGT-A methods in the Helios Sanatorium have been increasing the success rate by more than 20% for a long time – the chance of pregnancy is up to 70 % with one transfer of one examined embryo.
Long-term statistics show that PGT-M / PGT-A and embryo transfer without genetic abnormalities are a major breakthrough in the success of IVF cycles.
Does Preimplantation Genetic Testing increase the overal succes of IVF cycles?
Despite the fact that high-quality blastocysts are formed (developmental stage on the 5th and 6th day of embryo development) and both parents are genetically fine (they have a normal karyotype), genetically defective embryos may arise.
Such embryos may stop developing very early, but these errors may also be the reason why the embryo (in terms of development and morphology) does not implant in the womb, or pregnancy occurs, but the embryo is aborted very early.
Elder women develop significantly more chromosomally abnormal blastocysts than younger women – according to our results, younger women (under 35) develop on average about a third of genetically abnormal embryos, while women over 34 are genetically abnormal after PGT-M / PGT examination marked almost every second embryo.
If embryos after PGT-M and PGT-A examination are reported as genetically abnormal, such genetically defective embryos get excluded from further use, thus increasing the success rate and reducing the time required to achieve healthy pregnancies.
If embryos are identified as genetically abnormal after PGT-M / PGT-A testing, such genetically defective embryos are excluded from further use, thereby increasing success and reducing the time required for a healthy pregnancy.