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 PGD and PGS testing using NGS and PCR methods. PGD and PGS of good quality increase your chances of getting pregnant by more than 30 %.
The difference between Preimplantation Genetic Screening (PGS) and Preimplantation Genetic Diagnosis (PGD)
PGS is in fact searching for any change in the genetics of the embryo. Using the PGS methods we check all the DNA in its major sections at the level of chromosomes, or their parts. In our laboratory, we use for the PGS the NGS, sequencing of the new generation, which allows complete and accurate screening of all 24 chromosomes in the embryo’s genetic equipment. Deviations in the number or structure of chromosomes can most often lead to spontaneous abortion in the early stages of pregnancy or the birth of a child with severe disabilities. The most well-known syndrome is the Down syndrome caused by chromosome 21, Edwards syndrome (chromosome 18), Patau syndrome (chromosome 13), Turner syndrome (missing one copy of chromosome X), and Klinefelter syndrome (XXY chromosome condition).
Embryos selected by the new generation sequencing have a higher probability of attachment and further correct fetal development in the mother’s uterus. Women are thus spared of unnecessary embryo transfer and possible subsequent reproductive loss due to the non-standard genetic equipment of the embryo.
NGS is also intended for parents who are carriers of a balanced form of translocation, i.e., the reconstruction of genetic material between chromosomes. The method can offer them an embryo selection that does not translate into an unbalanced form of translocation, a form associated with multiple fetal losses or the birth of an affected offspring.
With PGD it comes to finding the specific genetic changes – mutations. PGD methods are designed also for parents, who are carriers of balanced translocation forms – reconstructions of genetic material between chromosomes. We can offer them PGD embryo selection, which will not bear unbalanced translocations forms associated with multiple fetal losses, or births of disabled children.
Why PGD and PGS
The large majority of reproductive losses (about 80%) or when embryos do not implant in the uterus may be caused by the so-called chromosomal aberration i.e. pathological changes in the DNA of the embryos. These can develop by wrong embryo cell division, for various reasons. It was also proven that the number of chromosomal aberrations in the germ cells increases with age. PGS method is then of great help in the selection of embryos without these chromosomal aberrations. It can also increase the likelihood of its implantation and proper development in the womb. Methods for PGD allow to exclude specific embryos carrying severe diseases (in case of monogenic diseases), or to exclude embryos carrying unbalanced changes in the DNA (in case of translocations).
A great benefit of PGS/PGD are also financial savings. In Sanatorium Helios we use the extended cultivation, when the 5th or 6th day of embryodevelopment is reached only by the best quality embryos. Thus we minimize number od transfers of embryos with chromosomal abnormalities associated with miscarriages. Reduction in psychological stress that is often associated assisted reproduction is also minimized.
Can I be sure to have a healthy baby using PGD and PGS?
A big plus of PGS/PGD resides mainly in the selection of embryos and increasing the likelihood of pregnancy to occur. In one female menstrual cycle, this probability is about 25% depending on the age of a woman. Thanks to techniques used in PGS/PGD the likelihood of getting pregnant is up to almost 75% after a transfer of a single embryo. In case of PGS we select embryos without major changes in the genetic material, ie primarily changes in chromosome number, and then women are spared of unnecessary embryotransfers, and subsequent reproductive losses due to the lack or oversupply of chromosomes. In case of PGD, there is a 99% probability that an embryo does not carry the specific disease for which it had been tester, or that it does not have unbalanced translocations. However, there is of course a possibility that in utero occur events with effect on the genome. Whether they are different infections, or physical causes. The risk of birth with any of malformations therefore always exists. The risk of birth of a child with some kinds of conditions in human population is about 3-5% of live births. These congenital defects includ even minor defects such as less severe cleft palatale defects, etc.
How is PGD/PGS Performed?
These biopsied cells are subsequently tested by a pre-chosen method. Healthy embryos are transferred in the patient’s uterus, or frozen and thus preserved for future use.
PGD methods used in Sanatorium Helios increase long-term success rates by over 20%. The odds of pregnancy after a single embryo transfer after PGD is about 70%.
Does Preimplantation Genetic Screening increase the overal succes of IVF cycles?
Although we are able to achieve blastocysts of a good quality (developmental stage of the fifth and sixth day of embryo development), and both parents are genetically fine (having a normal karyotype) genetically defective embryos may occur.
Such embryos may stop developing very early, but these errors can 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 very early aborted.
For women of more advanced age there is a significantly larger number of chromosomally abnormal blastocysts compared with younger women – according to our results in younger women (under 35) there is on average about a third of genetically abnormal embryos, while among women over 34 there is after PGD/PGS aCGH testing marked as a genetically abnormal almost every other embryo.
If embryos after PGD/PGS 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.
Would you like to learn more? Make an appointment for a consultation with our fertility experts.
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