Breaking Down the Types of Preimplantation Genetic Testing: PGT-A, PGT-M, and PGT-SR
Embarking on the path to parenthood is a journey filled with pivotal choices, each holding the promise of shaping your family's future. When pursuing parenthood via in vitro fertilization (IVF), there are many considerations that hopeful parents must contend with, including the choice of whether or not to have their embryos tested using preimplantation genetic testing (PGT).
PGT involves scraping a few cells from the embryo's outer layer during the blastocyst stage and analyzing them for chromosomal and genetic abnormalities. Depending on the circumstances, PGT can provide answers to your fertility questions and ultimately lead to improved IVF outcomes and successful live births. There are three different types of PGT. In this blog post, we’ll explore each type and discuss who should consider undergoing PGT for their fertility journey.
Preimplantation Genetic Testing for Aneuploidy (PGT-A)
PGT-A, previously called preimplantation genetic screening (PGS), is used to analyze an embryo’s number of chromosomes. These structures, made of protein and deoxyribonucleic acid (DNA), are found within animal and plant cell nuclei. Passed on from parents to offspring, chromosomes contain a person’s entire body of genetic information. Humans have 23 pairs of chromosomes, for a total of 46, with one set coming from each parent. For a human to develop normally, at a minimum, they need the correct number of chromosomes.
Aneuploidy is when there is an abnormal number of chromosomes, which can ultimately disrupt embryo growth, development, and function. Aneuploidy is also the most common cause of failed implantation or miscarriages and is also responsible for conditions like Down syndrome. PGT-A is often used to identify embryos with abnormal chromosome numbers so that only embryos with the correct number of chromosomes are used for transfer, thereby reducing the risk of miscarriage and eliminating aneuploid conditions.
Preimplantation Genetic Testing for Monogenic Disorders (PGT-M)
PGT-M, formerly called preimplantation genetic diagnosis (PGD), determines if embryos possess specific inheritable disorders. Parents who are carriers of a known genetic disorder, such as cystic fibrosis, Huntington’s disease, or Tay-Sachs disease, have up to a 50% chance of passing it on to a child. Using PGT-M with IVF may dramatically lower the risk of passing on genetic disorders.
Preimplantation Genetic Testing for Structural Chromosomal Rearrangement (PGT-SR)
PGT-SR is a type of genetic testing used to identify embryos that have chromosomal rearrangements, which is when embryos have the correct number of chromosomes, but the chromosomes themselves have structural abnormalities, including:
- Translocation: rearrangement of genetic material between two or more chromosomes
- Inversion: segments of a chromosome are reversed end to end
- Deletion: loss of a segment of a chromosome
- Insertion: when a segment from one chromosome is inserted into another chromosome
Individuals carrying these structural chromosomal rearrangements may have an increased risk of infertility, recurrent pregnancy loss, or the birth of children with chromosomal abnormalities. PGT-SR allows for the selection of embryos that have a normal chromosomal complement, reducing the risk of passing on these structural rearrangements to the offspring.
When Is PGT Recommended?
PGT is an immensely useful tool that can help improve many patients’ chances of successfully conceiving. This advanced form of assisted reproductive technology may be recommended for a wide variety of scenarios, including:
- Patients with known genetic disorders
- Patients with a history of recurrent pregnancy loss
- Patients of advanced maternal or paternal age
- Patients who have had unsuccessful IVF cycles in the past
- Patients who have a family history of genetic conditions
- Patients who have unexplained infertility
- Patients who have structural chromosomal abnormalities, which are typically discovered through genetic counseling
Consider Preimplantation Genetic Testing
Thanks to its ability to unveil genetic issues and mitigate risks, PGT stands as a valuable tool for those facing unique fertility challenges. Whether it’s addressing known genetic disorders, overcoming recurrent pregnancy loss, or ensuring a healthy start for future children, the power of PGT extends beyond conventional approaches. To learn more about IVF with PGT in New York City, contact Chelsea Fertility NYC to schedule a consultation.
