Preimplantation Genetic Testing (PGT) is a major advancement in assisted reproductive technology (ART), offering couples undergoing in vitro fertilisation (IVF) the opportunity to screen embryos for genetic abnormalities before transfer. However, it’s important to recognize that a PGT- euploid or normal embryo does not guarantee a successful pregnancy. Understanding PGT, its limitations, and the broader biological factors that influence fertility is important for setting realistic expectations.
What is PGT?
PGT screens embryos for chromosomal abnormalities after they reach the blastocyst stage (typically on day five to seven of development). A small number of cells from the embryo’s outer layer (destined to form the placenta) are biopsied and tested for chromosomal errors.
There are two primary types of PGT:
- PGT-A (Preimplantation Genetic Testing for Aneuploidy): Detects large chromosomal abnormalities, such as extra or missing chromosomes, which are often responsible for implantation failure and miscarriage.
- PGT-M (Preimplantation Genetic Testing for Monogenic Disorders): Identifies specific inherited genetic conditions based on a family’s known risk.
Couples may choose to undergo either test depending on their medical history and fertility goals, with the aim of improving the chances of a healthy pregnancy.
Misconceptions and Limitations of PGT
A common misconception is that a PGT- euploid or normal embryo guarantees a successful pregnancy or healthy baby. While PGT helps identify significant chromosomal abnormalities, it only tests a small sample of cells and does not account for smaller genetic mutations, cellular function, or overall embryo quality. It is not an absolute guarantee of the embryo’s viability.
Mosaicism, where an embryo contains both normal and abnormal cells, adds another layer of complexity. Some mosaic embryos can still lead to healthy pregnancies. For individuals who produce fewer embryos, understanding whether your clinic reports mosaicism is essential, as transferring a mosaic embryo might be a viable option. Working with a genetic counsellor to evaluate these risks and options can help make informed decisions.
PGT provides us with valuable information regarding chromosomal health but has limitations. It doesn’t guarantee successful implantation or rule out other issues that may affect fertility.
Complexities Beyond PGT
Even when a Euploid embryo is transferred, other biological factors can influence the outcome. Uterine abnormalities such as fibroids, polyps, or hydrosalpinx (fluid-filled fallopian tubes) may interfere with implantation. Additionally, underlying conditions like endometriosis or chronic inflammation can compromise endometrial receptivity.
There’s also emerging research into reproductive immunology, which examines how immune responses might affect embryo implantation. These complexities highlight that PGT is just one part of a multifaceted process, and overall reproductive health plays a significant role in determining success.
What to Do After a Failed Transfer of a Euploid ‘normal’ Embryo
If a transfer of a PGT – normal embryo does not result in pregnancy, it’s important to explore factors beyond the embryo’s genetics. A thorough evaluation of uterine health, underlying conditions such as endometriosis, and potential immune or inflammatory issues can provide important insights into why the transfer was unsuccessful.
Fertility success is influenced by many factors. PGT can significantly reduce the risk of transferring embryos with chromosomal abnormalities, particularly in women of advanced maternal age, but it doesn’t address other biological variables. A holistic approach to fertility, including assessing the uterine environment, ruling out infections or inflammation, and investigating endometrial receptivity, are necessary factors one might want to consider to improve the overall chances of success.
An insight from mamahood
PGT is a valuable tool in IVF, particularly for identifying chromosomal abnormalities that may lead to miscarriage or failed implantation. However, achieving a successful pregnancy often requires looking beyond just the genetics and considering all aspects of reproductive health, including the uterine environment, underlying conditions, and immune factors.
For personalised support and guidance through your fertility journey, Mamahood Health Advisors are here to help. Reach out via live chat or private message to discuss your next steps and explore all aspects of your reproductive health.
