PGT Genetic Testing in IVF: How It Works

Preimplantation Genetic Testing (PGT) is a group of laboratory techniques performed on IVF embryos before transfer to the uterus, as described by [ESHRE](https://www.eshre.eu/Guidelines-and-Legal/Guidelines/PGT). By analyzing a small biopsy of cells from the blastocyst, PGT can identify chromosomal abnormalities, single-gene disorders, and structural chromosomal rearrangements - allowing the fertility team to select the embryo with the highest potential for a healthy pregnancy.

Types of PGT

PGT-A (Aneuploidy Screening)

PGT-A tests whether each embryo has the correct number of chromosomes (46 in humans - 23 pairs). Embryos with too many or too few chromosomes (aneuploid) are the primary cause of IVF implantation failure, miscarriage, and chromosomal conditions. The rate of aneuploidy increases dramatically with maternal age:

• Age 30: ~30% of embryos are aneuploid
• Age 35: ~40% aneuploid
• Age 38: ~60% aneuploid
• Age 40: ~70-80% aneuploid
• Age 43+: ~90% aneuploid

"PGT-A does not create better embryos — it identifies the best embryos from the available pool. For patients over 35, where 40-80% of embryos may be aneuploid, this distinction is transformative. Instead of transferring embryos that will never implant, we can focus on those with genuine potential."
— WholeCares Partner Fertility Specialist

By identifying and selecting only euploid (chromosomally normal) embryos, PGT-A dramatically reduces the two most common adverse outcomes: failed implantation and miscarriage ([ASRM](https://www.asrm.org/topics/topics-index/genetic-screening-of-embryos/)).

PGT-M (Monogenic/Single-Gene Disorders)

PGT-M tests for specific inherited genetic diseases when one or both parents are known carriers ([Mayo Clinic](https://www.mayoclinic.org/tests-procedures/preimplantation-genetic-diagnosis/about/pac-20384707)). It requires custom probe design for each family - the testing protocol is tailored to the specific mutation being screened. Common indications:

• Cystic fibrosis (CFTR mutations)
• Sickle cell disease
• Thalassemia
• Huntington's disease
• BRCA1/BRCA2 (hereditary breast and ovarian cancer)
• Spinal muscular atrophy (SMA)
• Fragile X syndrome

PGT-SR (Structural Rearrangements)

For patients who carry balanced chromosomal translocations or inversions. These structural rearrangements increase the risk of producing embryos with unbalanced chromosomal content - leading to recurrent miscarriage or offspring with chromosomal abnormalities.

The PGT Process

1. Standard IVF cycle: Ovarian stimulation, egg retrieval, fertilization, and embryo culture proceed as in a regular IVF cycle.
2. Blastocyst biopsy (Day 5-6): When the embryo reaches the blastocyst stage, an embryologist removes 5-8 cells from the trophectoderm (the outer cell layer that will become the placenta). The inner cell mass (which becomes the baby) is not touched.
3. Vitrification: The biopsied embryo is immediately vitrified (frozen) while awaiting test results.
4. Genetic analysis: The biopsy sample is analyzed using Next-Generation Sequencing (NGS) - the most advanced and accurate platform currently available. Results take 1-2 weeks.
5. Results counseling: The fertility team reviews results with you, categorizing each embryo as euploid, aneuploid, or mosaic.
6. Frozen embryo transfer (FET): A frozen embryo transfer is scheduled for the best euploid embryo in a subsequent cycle.

The Mosaic Question

Mosaic embryos contain a mixture of normal and abnormal cells. They represent approximately 10-20% of tested embryos and create a clinical dilemma: should they be transferred?

Current evidence: low-level mosaicism (less than 40% abnormal cells) can result in healthy pregnancies, as the embryo may self-correct during development. High-level mosaicism carries higher risk. PGDIS (Preimplantation Genetic Diagnosis International Society) guidelines recommend discussing mosaic embryo transfer as an option when no euploid embryos are available - with appropriate genetic counseling.

Who Benefits Most from PGT?

• Women over 35: Higher baseline aneuploidy rate means PGT-A provides the greatest absolute benefit.
• Recurrent pregnancy loss: 2+ miscarriages - up to 60% of early miscarriages are caused by embryonic aneuploidy ([HFEA](https://www.hfea.gov.uk/treatments/explore-all-treatments/pre-implantation-genetic-testing-for-aneuploidies-pgt-a/)).
• Repeated implantation failure: 3+ failed transfers - selecting euploid embryos may solve the issue.
• Known genetic carriers: PGT-M is the only way to prevent transmission of known single-gene disorders without sacrificing the ability to have genetically related children.
• Single embryo transfer optimization: When you want to transfer one embryo for the best chance - PGT-A identifies which one.

At Wholecares partner fertility centers, PGT is performed using next-generation sequencing (NGS) technology with 98%+ accuracy. All three PGT types (PGT-A, PGT-M, and PGT-SR) are available. Transparent IVF pricing includes PGT costs in comprehensive packages, with results typically available within 10-14 days. Genetic counseling is provided before and after testing to ensure patients fully understand results and implications.

"The safety profile of trophectoderm biopsy is well-established. We're removing cells from the outer layer that becomes the placenta, not from the inner cell mass that becomes the baby. Millions of biopsies have been performed worldwide with no adverse effect on pregnancy rates or birth outcomes."
— WholeCares Partner Embryologist