Preimplantation Genetic Testing (PGT)
Genetic Assessment of Embryos During IVF
Preimplantation Genetic Testing (PGT) refers to genetic assessment performed on embryos created through in vitro fertilization (IVF) before embryo transfer.
PGT is used in selected clinical situations to assess embryos for chromosomal abnormalities, specific inherited genetic conditions, or structural chromosomal rearrangements.
The current terminology broadly includes:
- • PGT-A – assessment for chromosomal aneuploidy
- • PGT-M – testing for specific monogenic disorders
- • PGT-SR – testing for structural chromosomal rearrangements
The earlier terms PGS (Preimplantation Genetic Screening) and PGD (Preimplantation Genetic Diagnosis) have largely been replaced by the broader PGT terminology.
At Krishna IVF, preimplantation genetic testing is approached through individualized reproductive and genetic assessment in coordination with IVF treatment planning.
Understanding PGT
Embryos created during IVF may contain chromosomal abnormalities or inherited genetic defects that can influence embryo development, implantation, miscarriage risk, or inherited disease transmission.
PGT is intended to provide additional genetic information about embryos before transfer. The procedure involves embryo biopsy followed by laboratory-based genetic analysis.
PGT does not improve embryo quality or correct genetic abnormalities within an embryo. It is an assessment tool used in selected situations as part of reproductive and genetic counselling.
The decision to proceed with PGT should be individualized and based on clinical indication, reproductive history, and genetic evaluation where appropriate.
Types of Preimplantation Genetic Testing
PGT-A
PGT-A is used to assess embryos for abnormal chromosome number (aneuploidy).
Chromosomal abnormalities may influence:
- • implantation potential
- • embryo development
- • miscarriage risk
- • pregnancy continuation
PGT-A may be considered in selected situations depending on maternal age, recurrent implantation failure, recurrent pregnancy loss, previous embryo development patterns, or reproductive history.
PGT-M
PGT-M is performed when there is risk of transmission of a known monogenic disorder.
This may include inherited conditions such as:
- • thalassemia
- • muscular dystrophy
- • cystic fibrosis
- • sickle cell disease
- • Huntington disease
- • other identified familial genetic disorders
The test is designed specifically for the known mutation or disorder identified within the family.
PGT-SR
PGT-SR is used in selected patients with structural chromosomal rearrangements such as:
- • balanced translocations
- • inversions
- • other chromosomal structural abnormalities
The objective is to assess embryos for chromosomal imbalance associated with these rearrangements.
Who May Be Considered for PGT?
PGT may be considered in selected clinical situations, including:
- • recurrent pregnancy loss
- • repeated unsuccessful IVF cycles
- • advanced maternal age
- • known inherited genetic disorders
- • parental chromosomal rearrangements
- • severe male factor infertility in selected cases
- • previous pregnancies affected by genetic disease
- • selected cases involving recurrent embryo developmental abnormalities
Not every IVF cycle requires PGT, and it should not be considered a routine procedure for all patients undergoing assisted reproduction.
How PGT Is Performed
PGT is performed as part of an IVF cycle.
Ovarian Stimulation and Egg Retrieval
The IVF cycle begins with ovarian stimulation and egg retrieval after appropriate follicular development.
Fertilization and Embryo Culture
Eggs are fertilized in the embryology laboratory through conventional IVF or ICSI depending on clinical assessment.
Embryos are cultured in the laboratory until the blastocyst stage.
Embryo Biopsy
At the blastocyst stage, a small number of cells are removed from the trophectoderm layer of the embryo for genetic analysis.
The biopsy procedure is performed by trained embryology laboratory professionals using specialized laboratory techniques.
Genetic Analysis
The biopsied cells undergo genetic testing depending on the indication for PGT.
Laboratory techniques may include:
- • PCR-based analysis
- • next-generation sequencing (NGS)
- • other molecular genetic methods where appropriate
Embryo Transfer Planning
Embryo transfer planning is based on genetic findings, embryo development, clinical suitability, and reproductive treatment considerations.
Embryos may also be cryopreserved depending on laboratory workflow and treatment planning.
Limitations of PGT
PGT is a laboratory-based assessment tool and has important limitations.
Patients should understand that:
- • PGT does not guarantee implantation or pregnancy
- • chromosomally normal embryos may still fail to implant
- • abnormal embryos may arrest before transfer regardless of testing
- • embryo biopsy does not eliminate all biological uncertainty
- • not all genetic conditions can be assessed through PGT
- • mosaicism and biological variability may affect interpretation in some cases
The role and limitations of PGT should therefore be discussed carefully during reproductive and genetic counselling.
Genetic Counselling and Clinical Assessment
Genetic counselling forms an important part of treatment planning before PGT.
Assessment may include:
- • reproductive history review
- • pedigree chart analysis
- • parental genetic testing where indicated
- • previous pregnancy history
- • recurrent pregnancy loss assessment
- • chromosomal evaluation in selected patients
The decision to proceed with PGT should be based on individualized risk assessment and informed counselling rather than generalized use.
Clinical Approach at Krishna IVF
At Krishna IVF, preimplantation genetic testing is approached through coordinated reproductive medicine and embryology evaluation with attention to:
- • individualized clinical indication
- • reproductive history assessment
- • embryology laboratory coordination
- • genetic counselling where appropriate
- • evidence-based reproductive genetics practice
- • patient counselling regarding limitations and interpretation
The objective is to support informed reproductive decision-making through careful clinical and genetic assessment.
Important Considerations
PGT is not a guarantee of pregnancy or live birth.
Embryo implantation and pregnancy outcomes continue to depend on several factors, including:
- • age and ovarian reserve
- • egg quality
- • sperm quality
- • embryo developmental potential
- • uterine factors
- • hormonal and metabolic health
- • overall reproductive condition
Genetic testing provides additional information about embryos, but reproductive outcomes remain biologically complex and individualized.