Course / PGT-A and PGS Genetic Screening of Embryos
Preimplantation Genetic Testing for Aneuploidy (PGT-A), formerly and still commonly known as Preimplantation Genetic Screening (PGS), is an advanced laboratory technique used in conjunction with In Vitro Fertilization (IVF).
In simplest terms, PGT-A is a biopsy of the embryo. It allows us to analyze the chromosomes of an embryo created through IVF before it is transferred to the uterus (either to the intended mother or a gestational surrogate).
The Science Behind PGT-A:
Every human cell should contain 46 chromosomes—23 from the egg and 23 from the sperm. An embryo with this correct number is called euploid. An embryo with an missing or extra chromosome is called aneuploid. Most aneuploid embryos either fail to implant, result in a miscarriage, or can lead to conditions like Down Syndrome (Trisomy 21).
PGT-A helps us identify which embryos are euploid and have the highest potential for developing into a healthy pregnancy.
The Step-by-Step Medical Process:
IVF and Embryo Creation:Â Eggs are retrieved and fertilized with sperm to create embryos.
Embryo Biopsy:Â Around day 5 or 6 of development, the embryo forms a blastocyst, consisting of two cell groups: the Inner Cell Mass (which becomes the fetus) and the Trophectoderm (which becomes the placenta). Using a precision laser and micropipettes, an embryologist safely removes a few cells from the trophectoderm. This does not harm the inner cell mass and the biopsied embryo is then frozen (vitrified) to await test results.
Genetic Analysis:Â The biopsied cells are sent to a specialized genetics laboratory. The DNA from these cells is analyzed using advanced technologies like Next-Generation Sequencing (NGS) to count all 24 chromosomes (22 autosomes + X + Y).
Results & Reporting:Â The genetics lab provides a report classifying each embryo as:
Euploid:Â Chromosomally normal. The preferred candidate for transfer.
Aneuploid:Â Chromosomally abnormal. Not recommended for transfer.
Mosaic:Â A mix of both normal and abnormal cells. Transfer decisions for mosaic embryos are complex and require detailed genetic counseling.
The primary benefit of PGT-A is to empower intended parents and clinicians with critical information to make data-driven decisions, ultimately aiming to increase the efficiency and safety of the IVF and surrogacy process.
1. Increased Implantation and Pregnancy Success Rates:
By selecting a euploid embryo for transfer, we are transferring an embryo with the highest inherent potential for development. This significantly increases the likelihood of successful implantation, leading to higher pregnancy rates per transfer.
2. Reduced Risk of Miscarriage:
Chromosomal abnormalities are the leading cause of early pregnancy loss. Since many miscarriages are caused by aneuploid embryos, transferring a screened euploid embryo dramatically reduces the risk of miscarriage.
3. Decreased Time to a Successful Pregnancy:
Without PGT-A, multiple embryo transfers might be needed to achieve a pregnancy, with some transfers resulting in failure or miscarriage due to undetected aneuploidy. By identifying the best embryo first, PGT-A can help achieve a live birth faster by reducing the number of failed cycles.
4. Informed Family Balancing:
As the test analyzes the X and Y chromosomes, PGT-A can reveal the embryo’s genetic sex. This allows intended parents to make informed decisions regarding family balancing when transferring a single embryo.
5. Reduced Risk of Certain Chromosomal Disorders:
While not a replacement for prenatal testing, PGT-A significantly lowers the risk of having a child with certain chromosomal disorders like Down Syndrome (Trisomy 21), Edwards Syndrome (Trisomy 18), and Patau Syndrome (Trisomy 13).
6. Single Embryo Transfer (SET):
PGT-A provides the confidence to elect for a Single Embryo Transfer (SET). This is the gold standard of care as it completely avoids the risks associated with multiple pregnancies (twins, triplets), such as preterm birth, low birth weight, and preeclampsia for the gestational carrier.
While a powerful tool, PGT-A is not a perfect solution and is not recommended for every situation. A thorough understanding of its limitations is crucial.
1. It is a Screening Test, Not a Diagnostic Guarantee:
PGT-A is highly accurate, but no test is 100% infallible. There is a very small chance of a false positive or false negative result, or errors due to mosaicism (where the biopsied cells may not perfectly represent the entire embryo). We always recommend follow-up prenatal testing, such as NIPT or CVS, during pregnancy.
2. It Does Not Test for Specific Genetic Diseases:
PGT-A only screens for the number of chromosomes. It does not test for specific single-gene disorders like Cystic Fibrosis or Sickle Cell Anemia. For that, a different test called PGT-M (Preimplantation Genetic Testing for Monogenic Disorders) is required.
3. Potential for Embryo Damage (Theoretical Risk):
The biopsy process is performed by highly skilled embryologists and is considered very safe. However, any invasive procedure carries a minute, theoretical risk of damaging the embryo. Modern vitrification (freezing) techniques are excellent, and survival rates after thawing are very high.
4. Not All Embryos Are Suitable for Biopsy:
Only embryos that develop to the blastocyst stage (Day 5/6) are suitable for biopsy. In some cycles, especially with lower egg numbers, not all embryos may reach this stage, leaving no embryos to test.
5. The Possibility of No Transferable Embryos:
This is one of the most emotionally challenging outcomes. PGT-A may reveal that all embryos in a given cycle are aneuploid. While this news is difficult, it provides a clear explanation for previous IVF failures and prevents the heartache and cost of transferring embryos with no potential for a live birth.
6. The Cost:
PGT-A adds a significant additional cost to the IVF process, including fees for the biopsy procedure and the genetic laboratory analysis. Intended Parents must weigh this financial investment against the potential benefits of a more efficient journey.
7. The Complexity of Mosaic Results:
The discovery of mosaic embryos presents a complex ethical and medical dilemma. The decision to transfer or not transfer a mosaic embryo requires in-depth genetic counseling, as the potential outcomes can vary widely.
Our job is to listen, to connect the dots between your needs, and to determine how we can best help you have your baby. If you’re asking how much does it cost for a surrogate, we’ll walk you through every step of the process to ensure there are no surprises.
To make an appointment with one of our counselors or physicians, please call (212) 661-7673 or email info@surrogacy4all.com. We look forward to hearing from you.
Surrogacy4All is a unique international surrogacy service targeted at providing state of the art IVF and surrogacy services to Intended Parents irrespective of age, sex or color, at the lowest possible cost in the world.
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