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The world of assisted reproductive technology has seen remarkable advancements over the past few decades. From the inception of in vitro fertilization (IVF) in the late 1970s to the beginning of preimplantation genetic testing (PGT) of embryos, the ability to detect genetic abnormalities before an embryo transfer has redefined the possibilities of human reproduction in more ways than one.
Now let’s dive into the science behind preimplantation genetic testing and how it became what it is today!
The history of IVF
In 1978, Louise Brown, the world's first "test-tube baby," was born in the United Kingdom. A few years later, in 1981, came Elizabeth Carr, the first IVF baby in the U.S. and Head of Marketing, Public Relations, and Patient Advocacy for Genomic Prediction. These groundbreaking successes captured global attention and sparked significant advancements in reproductive medicine.
Since then, IVF has undergone numerous refinements and improvements, including techniques like intracytoplasmic sperm injection (ICSI), embryo freezing, and more, expanding its success rates and applications.
For the past 45 years, IVF has provided hope to millions of couples struggling with infertility worldwide, as well as offering new avenues to conceive for those in the LGBTQ+ community. Still, the ability to assess embryos for genetic health was a concept that took a bit more time to materialize.
The evolution of PGT testing
In the 1980s, initial attempts at diagnosing genetic disorders within embryos emerged, albeit through primitive techniques such as blastomere biopsy, involving the extraction of cells from developing embryos. However, these early methods were limited and posed significant risks to the embryos.
The 1990s witnessed a significant leap forward with the advent of more sophisticated genetic screening methods. Technologies like Polymerase Chain Reaction (PCR) and Fluorescence In Situ Hybridization (FISH) emerged, allowing for targeted genetic analysis in embryos. These new technologies not only enabled the identification of numerical chromosome abnormalities (think Trisomy 21), but they also allowed for DNA amplification for analysis.
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1992 was a milestone year with the first birth of a “normal” girl following IVF and preimplantation diagnostic testing for cystic fibrosis – while in pop culture compact discs surpassed cassette tapes as the preferred medium for recorded music.
Navigating ethical concerns
It’s important to note that with the strides in PGT technology, around this time ethical debates began to surface. The conversation around the ethical ramifications of discarding embryos found to carry genetic abnormalities raised complex questions about the sanctity of life, while legal frameworks varied globally, leading to ongoing discussions on the regulation of PGT.
Refinement and expansion
Still, PGT techniques continued to undergo refinement, culminating in more accurate and less invasive procedures. Comprehensive Chromosome Screening (CCS) and Comparative Genomic Hybridization (CGH) broadened the scope of chromosomal abnormality screening, significantly enhancing the selection of healthy embryos.
A big moment for PGT arrived with the advent of Next-Generation Sequencing (NGS) technologies. This revolutionary advancement offered higher resolution and accuracy in detecting genetic anomalies within embryos and became pivotal in identifying a wider spectrum of genetic mutations and structural variations.
It was then that PGT branched into categories like PGT-A (aneuploidy screening), PGT-M (monogenic/single-gene disorders), and PGT-SR (structural rearrangements), opening the door for individuals and couples looking to reduce their risk of miscarriage and prevent the risk of inherited genetic disorders.
The road ahead
Today, recent advancements continue to shape the future of PGT, including the implementation of high-throughput SNP array technology, which studies have shown leads to fewer false negatives and false positives than NGS-based methods.
Additional tests have also come into play, many of them not even requiring an additional embryo biopsy. For example, PGT-A+ is an enhanced test offered by LifeView that can determine the origin of an embryo’s chromosome abnormality (sperm or egg) with an accuracy rate of 98-99%. The only additional requirement is saliva samples from the patient, partner, and/or gamete donor in addition to embryo samples.
Another option called Preimplantation Genetic Testing for Polygenic Risk (PGT-P) is a genetic screening technique that can help determine the potential risks for various adult-onset conditions like diabetes, cancers, schizophrenia, and even heart disease. Also called the Embryo Health Score test, it allows you and your clinician to compare overall disease risks among embryos and make decisions about which embryo to prioritize for transfer.
Knowledge is power
The history of preimplantation genetic testing during IVF reflects a remarkable journey of scientific innovation, ethical dilemmas, and ongoing advancements. From humble beginnings in genetic diagnosis to the sophisticated methods available today, PGT has transformed assisted reproduction, offering hope to individuals facing genetic concerns while reducing the risk of miscarriage and increased pregnancy rates in others. With even more breakthroughs on the horizon, when it comes to IVF and PGT testing, the future is bright.
If you’re considering IVF with preimplantation genetic testing (PGT), be sure to consult with your fertility specialist and Genetic Counselor on the different types of genetic testing and platforms. With the proper education and counseling, rest assured that you’ll make the best possible decision for you and your family.
Kristyn Hodgdon is the Co-Founder and Chief Creative Officer at Rescripted.
