Pros and Cons of Preimplantation Genetic Screening (PGT-A/PGS)

PGT-A (Preimplantation Genetic Testing for Aneuploidy) is a laboratory procedure performed during IVF to analyze embryos for chromosomal abnormalities before they are transferred to the uterus.

PGT-A is one of several forms of preimplantation testing. Another, called PGT-M (Preimplantation Genetic Testing for Monogenic Diseases), is used to identify specific inherited conditions caused by single-gene mutations, such as cystic fibrosis, Tay-Sachs disease, hemophilia, or sickle cell anemia. PGT-A, by contrast, focuses only on chromosomal number and structure, not individual gene disorders.

During the IVF process, embryos develop for several days in the lab. On day 5 or 6, a few cells are carefully removed from the outer layer (the trophectoderm) and sent for genetic analysis. The embryo is then frozen while the results are processed.

PGT-A screens for:

• Aneuploidy (abnormal number of chromosomes)
• Trisomies such as Down syndrome (Trisomy 21)
• Monosomies like Turner syndrome
• Other chromosomal imbalances that can lead to implantation failure or miscarriage

PGT-A is a tool, not a guarantee. When integrated into an IVF treatment plan, it helps prioritize which embryos to transfer first, potentially improving efficiency and outcomes.

A study in the Journal of Assisted Reproduction and Genetics found that women who underwent PGT-A had higher ongoing pregnancy rates per transfer compared to those who did not use genetic screening. The benefit was most pronounced in women over 37. However, another large trial published in The New England Journal of Medicine found no significant difference in live birth rates after one full IVF cycle when comparing PGT-A to conventional embryo selection in women aged 20-37.

These findings suggest PGT-A may improve outcomes for specific patient groups but may not benefit everyone equally. The decision to use PGT-A should be personalized based on age, embryo quantity and quality, and reproductive history.

Many fertility centers now perform PGT-A using Next Generation Sequencing (NGS). NGS is a more advanced method of analyzing embryo DNA, offering greater accuracy, detecting mosaicism more precisely, and providing a higher-resolution view of chromosomal health. It can also be combined with PGT-M when both chromosomal and single-gene testing are needed.

Pros:

• Reduces miscarriage rates by identifying chromosomally abnormal embryos
• Increases chances of successful implantation per transfer
• May reduce the time to pregnancy by avoiding transfers of abnormal embryos
• Allows for confident single embryo transfer, reducing multiple pregnancy risks
• Provides reassurance for patients with age-related or genetic concerns
• May be used for family balancing (sex selection) in certain cases, depending on patient preference and clinic policy

Cons:

• Adds significant cost to IVF treatment
• Involves embryo biopsy, which carries a minimal but non-zero risk
• Accuracy limitations due to mosaicism and testing errors
• May result in discarding embryos that could have led to healthy pregnancies
• Does not guarantee pregnancy or eliminate all risks of miscarriage or birth defects

Not everyone undergoing IVF needs genetic screening. PGT-A is most commonly recommended for:

• Women age 35 and older
• Patients with recurrent miscarriages
• Couples with known genetic risks
• Multiple failed IVF cycles
• Patients wanting to maximize success per transfer
• Couples pursuing family balancing (sex selection)

While PGT-A is generally safe, it is not without limitations and potential risks (as any procedure carries):

• False positives and false negatives due to mosaicism or sampling error
• Although embryo biopsy is considered safe when performed by experienced embryologists, it is not entirely risk-free
• PGT-A is not 100% accurate. Mosaicism (when an embryo contains both normal and abnormal cells) can lead to discarded embryos that might have resulted in healthy pregnancies. Some studies suggest 20–40% of embryos are mosaic.
• A chromosomally normal embryo may still fail to implant if other factors, including uterine health and embryo quality, are suboptimal.
• Testing may result in discarding embryos labeled abnormal that could have self-corrected or resulted in healthy births.

It’s also important to note that embryo appearance alone isn’t always a reliable indicator of genetic health. Even embryos that look ideal under the microscope can carry chromosomal abnormalities. Genetic testing, especially when performed through NGS, provides a more accurate assessment of embryo viability.

• The Preimplantation Genetic Screening Pros and Cons ultimately depend on your unique medical situation, age, and treatment goals.
• The PGT-A can be a valuable tool for reducing miscarriage risk and improving embryo selection, particularly for older patients or those with recurrent pregnancy loss.
• It is not necessary or beneficial for everyone, and the added cost and potential limitations should be carefully considered.

Patients come first at New Hope. We strive to provide the best fertility care, from maintaining the highest medical, scientific, and academic standards to supporting you through every stage of your journey to parenthood.

One of the most important aspects of New Hope Fertility care is that we custom-design our fertility treatments to the individual. If you’re ready to learn more or get started, call us at (347) 970-8479 or book an appointment online.