Preimplantation Genetic Testing for Aneuploidy (PGT-A):
Detecting Chromosomal Abnormalities in Embryos

What is PGT-A?

Preimplantation Genetic Testing for Aneuploidy (PGT-A) is an advanced technique in assisted reproduction that analyses all 23 pairs of chromosomes in embryos, allowing the identification of those with the correct chromosomal makeup. Discover how PGT-A can improve implantation rates and reduce the risk of miscarriage in assisted reproduction treatments.

PGT-A revolutionises assisted reproduction by detecting chromosomal abnormalities in IVF or ICSI embryos before they are transferred to the uterus. This advanced analysis significantly increases implantation success rates and reduces the risk of miscarriage, ensuring a higher likelihood of a healthy pregnancy. Aneuploidies, such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome), are among the most common chromosomal abnormalities detected by PGT-A.

How is PGT-A performed?

The PGT-A process follows a series of key steps that allow the embryo to be analysed without compromising its development:

1. Ovarian stimulation and embryo collection: Controlled stimulation is performed to retrieve multiple oocytes, which are fertilised in the laboratory through in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI).
2. Embryo culture: The embryos are cultivated in optimal laboratory conditions until they reach the blastocyst stage, usually on day five.
3. Trophectoderm biopsy: A few cells are extracted from the outer layer (trophectoderm) of the blastocyst, without affecting the inner cell mass that will develop into the baby.
4. Genetic analysis: The extracted cells are analysed using advanced next-generation sequencing (NGS) techniques to detect possible chromosomal abnormalities.
5. Transfer of a healthy embryo: If a euploid embryo (one without chromosomal abnormalities) is identified, it is transferred to the mother’s uterus to increase the chances of implantation and a successful pregnancy.

Using next-generation sequencing (NGS), PGT-A examines all 23 pairs of chromosomes in the blastocyst to identify numerical abnormalities, known as aneuploidies. The selection of euploid embryos, which have the correct number of chromosomes, is crucial for reproductive success. Recent advancements in NGS, as highlighted by Morales (2023), allow for the detection of mosaic embryos or partial aneuploidies, providing a more comprehensive and precise analysis. It is important to note that approximately 44.9% of embryos produced in an IVF cycle are aneuploid (Yang et al., 2012), and the likelihood of these abnormalities increases exponentially after the age of 35.

Benefits of PGT-A in Fertility Treatments

Incorporating PGT-A into assisted reproduction treatments offers multiple advantages:

• Increased success rate: By transferring only embryos with a normal chromosomal complement, implantation rates improve, increasing the probability of pregnancy per transfer.
• Reduced risk of miscarriage: Aneuploidies are one of the leading causes of miscarriage in the first trimester. PGT-A helps minimise this risk by selecting embryos without chromosomal abnormalities.
• Option for single embryo transfer: Thanks to the selection of viable embryos, it is possible to opt for the transfer of a single embryo, reducing the risks associated with multiple pregnancies.
• Optimised time to pregnancy: By quickly identifying the most suitable embryos, the number of transfers required to achieve a viable pregnancy is reduced, making the process more efficient and cost-effective in the long run.

Who Can Benefit from PGT-A?

PGT-A is recommended for all couples undergoing assisted reproductive treatments, as any pregnancy carries a risk of chromosomal abnormalities. However, certain groups may particularly benefit:

• Women of advanced maternal age: The incidence of aneuploidies increases with age, making PGT-A particularly useful for women over 35.
• Couples with a history of recurrent miscarriages: Identifying chromosomally normal embryos can reduce the likelihood of repeated pregnancy loss.
• Cases of repeated implantation failure (RIF): PGT-A can help determine whether aneuploidies are the underlying cause of previous IVF failures.
• Couples with previous IVF failures: PGT-A can help establish whether past failures were due to embryonic factors or other causes, such as endometrial receptivity.
• Couples with a history of chromosomal abnormalities: Those who have had children or previous pregnancies affected by chromosomal abnormalities may consider PGT-A to increase the chances of a healthy pregnancy.

Final Considerations Before Choosing PGT-A

If you are considering PGT-A as part of your fertility treatment, it is essential to discuss its benefits and limitations with a specialist in assisted reproduction. While it offers clear advantages in specific cases, its application should be individually assessed.

At our clinic, we are committed to excellence and precision. Our PGT-A test is accredited by ENAC with certification number 1497/LE2766, meeting the requirements of the UNE-EN ISO 15189 standard. This accreditation is a mark of trust that supports our commitment to the health and well-being of the families who place their confidence in us, ensuring the highest quality and reliability in every analysis.

If you would like to learn more about how to improve your chances of pregnancy, we invite you to schedule a consultation with a fertility specialist.