Preimplantation Genetic Testing ( PGT )

Preimplantation Genetic Testing ( PGT )

Preimplantation genetic testing (PGT) is a cutting-edge procedure used to identify genetic abnormalities in embryos created with in vitro fertilization (IVF). The goal of PGT is to allow your physician to select embryos predicted to be free of a specific genetic condition or chromosome abnormalities for transfer.

PGT for Aneuploidies (PGT-A)

• Aneuploidy is the occurrence of a wrong number of chromosomes in a cell, for example, 45 or 47 chromosomes instead of the usual 46.
• Embryo aneuploidies may be responsible for implantation failures, miscarriages and affects IF outcomes.
• PGT-A consists in an IVF cycle where embryos are biopsied and screened for chromosomal aneuploidies prior to replacement into the uterus.
• PGT-A is aimed at avoiding the transfer of chromosomally abnormal embryos to minimize implantation failures and miscarriages

Indications:

• Advanced maternal age (AMA)
• Recurrent implantation failure (RIF)
• Recurrent Miscarriage (RM). It should be noted that couples with a history of RM have a high chance of successfully conceiving naturally and that PGT-A for RM without a genetic cause is not recommended in a recent evidence-based guideline (The ESHRE Guideline Group on RP L et al., 2018)
• Severe male factor (SMF)

PGT for Structural Rearrangements (PGT-SR)

• Chromosomal rearrangements can be inherited or may occur spontaneously (denovo).
• Carriers of balanced rearrangements can pass down the same rearrangement or may produce embryos with unbalanced chromosome rearrangements, resulting in pregnancy loss or child with genetic abnormalities.
• PGT-SR reduces the risk of having a pregnancy or child with an unbalanced structural abnormality.

PGT for Monogenic/ single gene disorders (PGT-M)

• Pre-implantation Genetic Testing for monogenic disorders using target sequence enrichment.
• NGS based testing with linkage analysis to enhance detection of pathogenic variants
• Combined PGT -A and PGT-M in a single workflow
• A fully informative STR marker will have different amplicon sizes for each of the four parental alleles, allowing discrimination of all possible embryo genotypes and detection of problems of contamination, ADO, recombination and copy number aberrations

Inheritance pattern

Autosomal Dominant

One mutated copy is enough to cause the disease couple who either of them aare affected , in each pregnancy there is a 50% chance of child being affected and 50% unaffected

Autosomal Recessive

Two mutated copy is required to cause the disease couple who carriers, in each pregnancy there is a  25% chance of child being affected and 50% unaffected