Preimplantation Genetic Testing (PGT)
Preimplantation genetic testing (PGT) makes it possible to examine embryos created through in vitro fertilisation (IVF) before they are transferred to the uterus. The aim is to detect genetic abnormalities that lead to early miscarriage or to harm the fetus, and to ensure that only healthy embryos with a better chance of a successful pregnancy are transferred.
Who Is PGT Suitable For?
PGT can be helpful if you are concerned about hereditary conditions or complications in pregnancy, because it identifies genetic problems before the embryo is transferred to the uterus. Consider PGT if:
- You or your partner carry a genetic mutation that you would prefer not to pass on to your future child.
- You or your partner carry a genetic mutation that you would prefer not to pass on to your future child.
- A previous pregnancy of yours was affected by genetic abnormalities.
- You are over 35 and want to reduce the risk of genetic abnormalities such as Down syndrome.
- You have experienced recurrent miscarriages or several unsuccessful IVF attempts.
- Your partner has issues with sperm quality and you are planning to use ICSI.
- One of you has recently undergone cancer treatment.
- You need HLA typing to have a child who could help in the treatment of an affected sibling.
PGT increases the likelihood of transferring an embryo with a favourable genetic result and therefore the chance of the birth of a healthy child. It is not, however, a universal guarantee, so we always carefully choose the right type of testing, clearly explain its possibilities and limitations, and recommend the next steps according to each couple's situation.
Our goal is for you to understand the whole process, feel more confident, and be able to make informed decisions. We will guide you through each step with care, expertise, and the greatest possible respect for your situation.
What Are the Types of PGT and When to Choose Each?
There are several types of PGT, depending on the genetic risk being assessed in the embryo. The three main categories are:
- PGT-M is used in couples with an increased risk of a specific hereditary condition caused by a change in a single gene.
- PGT-SR is intended for couples in which one partner carries a chromosomal rearrangement, such as a translocation or inversion, which can result in an unbalanced chromosomal set in the embryo.
- PGT-A assesses the number of chromosomes in the embryo.
We always select the appropriate type of PGT based on the couple's specific genetic situation, medical history, the results of previous examinations, and the course of the IVF treatment.
PGT-A: Preimplantation Genetic Testing for Aneuploidy
PGT-A is a genetic examination of chromosomal abnormalities in the embryo before transfer to the mother's uterus. It helps determine whether the embryo has the correct number of chromosomes. If a chromosome is missing or, conversely, present in addition, we speak of aneuploidy.
Embryos with an incorrect number of chromosomes often fail to implant in the uterus or can lead to early pregnancy loss. In rare cases, a chromosomal abnormality may also result in the birth of a child with a genetic condition such as Down syndrome.
The risk of aneuploidy increases markedly around the age of 35 in women, when the chance of finding an embryo with the correct number of chromosomes rapidly declines. Shortly before the onset of menopause, aneuploidy is present in practically every oocyte.
Who Is PGT-A Suitable For?
PGT-A is recommended and indicated by a clinical geneticist primarily in situations where there is an increased risk of a chromosomal abnormality in the embryos, for example:
- the woman is over 35,
- recurrent pregnancy loss,
- repeated IVF failures
- the birth of a child or a miscarriage of a fetus with a chromosomal abnormality,
- mosaic variations in the number of sex chromosomes in one of the partners,
- severe disorders of sperm production in the male partner,
- chemotherapy or radiotherapy previously undergone by one of the partners.
PGT-A can therefore help select an embryo with a normal chromosome count, increase the likelihood of a successful transfer, and reduce the risk of early miscarriage. This shortens the time needed to achieve a successful pregnancy and the birth of a healthy child.
What Do the Test Results Look Like?
Examined embryos can be divided into four basic groups based on the examination outcome and the recommendation for further steps:
Embryo Recommended for Transfer to the Uterus
- euploid embryos with a normal result
- standard prenatal care and screening are recommended in the event of pregnancy
Embryo Recommended for Transfer to the Uterus After Consultation With a Clinical Geneticist
- mosaic embryos
- embryos with segmental aneuploidy, where the abnormality involves only part of a chromosome
- there is a risk of aneuploidy and an increased risk of miscarriage, but also a chance of a normal pregnancy
Embryo Not Recommended for Transfer to the Uterus
- aneuploid embryos with an incorrect number of chromosomes (monosomy or trisomy), where the abnormality involves an entire chromosome
No Result Could Be Obtained for the Embryo and It Remains Genetically Untested
- in 3 to 5 % of embryos a result cannot be obtained
- the examination can be repeated from a newly taken sample
- the embryo can be transferred without testing (as in cycles without PGT-A)
What Are the Limitations and Reliability of PGT-A?
- According to current knowledge, biopsy of the embryo on day 5 to 6 of development at the blastocyst stage poses no risk to the fetus or to the child once born. It also does not reduce the embryo's chance of surviving freezing or of successful implantation in the uterus.
- In a small proportion of cases (3 to 5 %) it may be difficult to obtain a result of the genetic examination due to handling of a small sample and the low number of cells available for analysis. In such cases the embryo can be thawed again and the examination repeated, or the couple may decide to transfer the embryo without testing.
- PGT-A can identify embryos suitable for transfer with an accuracy of more than 97 %, but it cannot detect defects caused by random mutations or developmental abnormalities without a clear genetic cause, which can also occur in natural pregnancies (3 to 5 %). For this reason, the same prenatal care is recommended after a PGT-A pregnancy as in any other pregnancy.
- Biopsied trophectoderm cells do not always fully represent the genetic make-up of the rest of the embryo. In 5 to 10 % of embryos, random genetic changes may occur that typically disappear during further development (mosaic aneuploidies, segmental chromosomal aneuploidies). Although these abnormalities may be associated with certain risks, the embryo still has meaningful potential for a successful pregnancy and the birth of a healthy child. Their transfer to the uterus is therefore still possible following consultation with an IVF specialist and a clinical geneticist.
- If only a few blastocyst-stage embryos are available, it may turn out that all of them carry a chromosomal abnormality. PGT-A reveals this fact but neither causes it nor can correct it.
PGT-M: Preimplantation Genetic Testing for Monogenic Disorders
PGT-M is a genetic examination of embryos intended for couples with a known risk of a specific hereditary condition caused by a change in a single gene. This may include, for example, cystic fibrosis, spinal muscular atrophy, Huntington's disease, certain hereditary cancer syndromes, or other serious genetic diagnoses in the family.
The aim of PGT-M is to select for transfer an embryo in which the specific genetic change associated with the given disease has not been detected. The examination can thus significantly reduce the risk of the birth of a child with a serious hereditary condition.
Who Is PGT-M Suitable For?
PGT-M may be particularly appropriate when:
- one or both partners carry a known genetic variant associated with a hereditary condition,
- a serious monogenic disease occurs repeatedly in the family,
- the couple already has a child with a genetically determined condition,
- genetic testing has shown a risk of transmitting a specific disease to offspring.
PGT-M is always prepared individually according to the specific genetic diagnosis in the family. A consultation with a clinical geneticist and the preparation of a laboratory protocol for the given family are therefore essential before the examination itself.
PGT-SR: Preimplantation Genetic Testing for Structural Chromosomal Rearrangements
PGT-SR is intended for couples in which one of the partners has been diagnosed with a structural chromosomal rearrangement, such as a translocation or inversion. The carrier of such a rearrangement may themselves be completely healthy, yet during the formation of eggs or sperm a higher proportion of embryos with an unbalanced chromosomal set may arise.
Embryos with an unbalanced chromosomal change often fail to implant, can lead to recurrent miscarriages, or, rarely, to the birth of a child with a chromosomal abnormality. The aim of PGT-SR is to select for transfer an embryo without an unbalanced chromosomal rearrangement.
Who Is PGT-SR Suitable For?
PGT-SR may be particularly appropriate when:
- one of the partners is a carrier of a balanced chromosomal translocation or inversion,
- the couple has experienced recurrent miscarriages,
- an unbalanced chromosomal abnormality of the fetus was diagnosed in a previous pregnancy,
- a chromosomal rearrangement linked to a reproductive risk has occurred in the family.
PGT-SR helps reduce the risk of transferring an embryo with an unbalanced chromosomal set. As with the other types of PGT, however, it does not guarantee a pregnancy or the birth of a healthy child. The result must always be interpreted in the context of the specific chromosomal rearrangement and the couple's overall situation.
How Does PGT Work?
Genetic Consultation With Indication for PGT
The process begins with a genetic consultation, where, based on the medical history and genetic findings, a decision is made on whether PGT is appropriate for the couple and which type of PGT is best suited.
IVF Cycle
All types of PGT require an in vitro fertilisation (IVF) cycle so that the embryos obtained can be examined genetically. The entire process begins after the initial consultation with the IVF physician and the onset of menstruation.
After 12 to 15 days of controlled ovarian stimulation, oocyte retrieval is performed.
Once the eggs have been fertilised with sperm, they are cultured up to the blastocyst stage, which the embryo usually reaches 5 or 6 days after retrieval.
Biopsy and Embryo Freezing
At this stage a biopsy is performed in which several cells (5 to 10) are taken from each embryo for genetic testing. The procedure is carried out by an experienced embryologist. The biopsied embryos are then frozen (vitrified) and await the results of the genetic testing.
Genetic Analysis
Trophectoderm biopsy samples are transferred for examination to our genetic laboratory GNTlabs by Gennet. The genetic analysis is carried out using PCR-based methods and state-of-the-art technologies such as next-generation sequencing (NGS) and GSA.B94
Test results are available in 2 to 4 weeks, depending on the type of test performed. In the event of a normal result, the embryo is transferred in a subsequent cycle.
Frozen Embryo Transfer (FET)
We then prepare the patient's uterus for embryo transfer. Suitable embryos are thawed and transferred to the uterus, while the remaining embryos are stored for possible future use.
What Are the Benefits of PGT?
The transfer of embryos with genetic abnormalities is often unsuccessful and can lead to miscarriage. If such a miscarriage occurs and a uterine cavity revision becomes necessary, the next embryo transfer attempt may be delayed by several months.
- Reduces the number of unsuccessful transfers, which also lessens emotional strain
- Reduces the number and risk of spontaneous miscarriages.
- Reduces the risk of a pregnancy involving a fetus with a chromosomal abnormality
- Helps avoid unnecessary embryo transfers, saving time and cost and speeding up the path to the birth of a healthy child
- Provides important information that can help you decide on the next steps in treatment, for example when choosing donor eggs, sperm, or embryos
Before opting for PGT, it is advisable to have a professional assessment of all the unique circumstances of the couple being treated. A consultation with an IVF specialist can help with this, and the specialist may then incorporate PGT into the treatment plan.
Frequently Asked Questions (FAQs)
Do you have further questions or would you like to book a consultation?
Which monogenic disorders can be tested by PGT?
We are able to test for all monogenic diseases, provided that the pathogenic genetic variant (mutation) causing the disease in the family has already been identified and can be specifically targeted in embryos. Each test is prepared individually for a specific family, gene, and mutation.
Before starting the IVF cycle, a consultation with a clinical geneticist is therefore always necessary, followed by laboratory preparation of the test. This may include additional testing of the partners or other family members and verification that the given mutation can be reliably detected in embryos.
Only after this step can PGT-M be safely included in IVF treatment.
Commonly tested diseases include, for example:
- Huntington’s disease
- Cystic fibrosis
- Thalassemia
- Duchenne muscular dystrophy
- Fragile X syndrome
- BRCA1/2 gene mutations (hereditary breast and ovarian cancer syndrome)
Can I use PGT for sex selection of the child?
Yes, but only in indicated cases. PGT is not used to choose the sex of a child according to the parents’ wishes. Czech law allows sex selection in assisted reproduction only in cases where it can help prevent a serious genetically determined disease linked to sex.
Typical examples include certain X-linked disorders, such as haemophilia or Duchenne muscular dystrophy, where the increased risk of developing the disease is associated with the male sex of the child.
Can PGT damage the embryo?
Taking a few cells from an embryo by an experienced embryologist is generally considered safe. Research indicates that the implantation probability is the same as that of a non‑biopsied embryo.
Who recommends PGT?
PGT can be performed only if recommended by a clinical geneticist and both partners are obliged to provide written consent.
Are PGT methods covered by health insurance?
If a clinical geneticist recommends PGT based on the indication criteria defined by the Society of Medical Genetics, then the test is covered by health insurance—even in cases where the IVF cycle itself is not covered (for example, for women over 40 or couples who have exhausted their covered cycle allotment). Couples typically pay only for additional micromanipulation techniques within the IVF cycle that are not covered by insurance. If the couple does not meet the criteria for insurance coverage of PGT, the geneticist may still indicate the test, but the couple will need to cover its full cost as per the clinic’s price list.
How much does PGT cost?
In situations where PGT‑A is not covered by insurance, we offer it as a self‑paid option. The price follows our clinic’s rate schedule, and we will gladly explain the details to you on request
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