PGT - Preimplantation Genetic Testing
The goal of preimplantation genetic testing (PGT) is to analyze embryos genetically before implantation in the uterus. Samples are taken from embryos created during IVF: 5–10 cells are extracted from day 5–6 embryos (blastocysts) and analyzed using next-generation sequencing.
PGT-A: Aneuploidy Testing
This method identifies aneuploidies, i.e., abnormalities in chromosome number or structure. It helps select embryos with a normal number of chromosomes, offering the best chance of successful implantation and healthy fetal development.
PGT-A reduces the number of cycles needed to achieve pregnancy and significantly lowers the risk of miscarriage.
Understanding Chromosomes and Aneuploidy
Normal Chromosome Structure
- Healthy human cells have 23 pairs of chromosomes (46 total)
- One set inherited from mother, one from father
- X and Y chromosomes determine biological sex
- Female: 46,XX
- Male: 46,XY
- Embryos with correct number are called euploid
Chromosomal Abnormalities (Aneuploidy)
- Missing, duplicated, or partly altered chromosomes
- May appear normal in early development
- Often fail to implant
- Lead to early miscarriage
- Rarely progress to congenital disorders
- Example: Down syndrome (extra chromosome 21)
Connection Between Aneuploidy and Maternal Age
Under 35 years: ~40% of embryos are aneuploid
Over 40 years: >70% are aneuploid (PGT-A data)
This explains why IVF success rates decrease and miscarriage risk increases in older women.
PGT Process
Embryo Development & Biopsy
- Embryos cultured for 5–6 days until blastocyst stage
- Biopsy performed on good-quality blastocysts
- Few trophectoderm (TE) cells removed
- TE cells form placenta (not the fetus)
- Inner cell mass (ICM) becomes the fetus
- Removing few TE cells does not harm embryo
Analysis & Transfer
- Embryos immediately frozen after biopsy
- Cells analyzed in specialized PGT laboratory
- Results pending before transfer decision
- Chromosomally normal embryos identified
- Frozen embryo transfer (FET) in next cycle
- Improved pregnancy success rates
Types of PGT Testing
PGT-M: Monogenic Disorders
Used to detect inherited single-gene (monogenic) disorders when one or both parents carry a known pathogenic gene variant.
Examples include cystic fibrosis, hemophilia, and Huntington's disease. It allows selection of embryos that do not carry the mutation, reducing the risk of inherited disease.
Understanding Monogenic Disorders
- Genes are fundamental units of genetic information
- Located in pairs on chromosomes 1-22 (autosomes)
- Also on sex chromosomes (XX in females, XY in males)
- Gene mutations can impair biological function
- Faulty genes passed to next generation
- Various inheritance patterns possible
Inheritance Patterns
- Autosomal dominant disorders
- Autosomal recessive disorders
- X-linked dominant disorders
- X-linked recessive disorders
- Y-linked disorders
- Genetic counseling for family planning
PGT-SR: Structural Rearrangements
- Detects unbalanced chromosomal rearrangements
- Screens for missing or extra chromosome segments
- Addresses parental structural abnormalities
- Improves ART outcomes for carriers
- Reduces risk of implantation failure
- Prevents congenital disorders in offspring
Advanced PGT Options
- PGT-HLA: HLA compatibility for sibling transplants
- PGT-P: Polygenic risk testing (limited availability)
- Assessment of complex disease risks
- Cardiovascular disease screening
- Cancer risk evaluation
- Diabetes susceptibility testing
Advanced Genetic Testing for Optimal IVF Outcomes
Our comprehensive PGT services provide cutting-edge genetic analysis to maximize your chances of a successful pregnancy and healthy baby, while minimizing risks of genetic disorders and pregnancy loss.
