Doctor Michael Doyle of the popular international IVF centre CT Fertility explains in layman’s terms how IVF technology continues to evolve and result in even better results for prospective gay parents.
The key challenge of IVF has always been to create the healthiest embryos possible and to identify the ones that are most likely to develop well and result in a successful pregnancy. Given the health risk of multiple births for both the carrier and the future babies, the goal is to transfer the lowest possible number (often only one now) and still achieve the maximal impact (highest pregnancy rate).
Twenty years ago the best we could do was to grow embryos for three days before implanting them into the carrier’s womb, as few would survive longer in the laboratory. However at that early stage of development it was impossible to predict which embryos would further develop, and that meant transferring a higher number of embryos and “hoping for the best.” Unfortunately often the result was no pregnancy, and when it was achieved, multiple pregnancies were common.
Patience is a virtue – also when it comes to embryo rearing
Over time, science gained a better understanding of the nutrient sources for embryonic development and skilled embryologists were able to sustain embryos for 5-6 days so they could reach the critical “blastocyst” phase. At this stage it is much easier to determine which embryos will result in healthy live births, based on their rate of cellular growth and other gradable qualities.
Even with these far more effective blastocyst transfers, however, it was demonstrated that many of these highly graded embryos still had chromosomal abnormalities that led to reduced implantation or increased miscarriage. This heralded our next breakthrough – the ability to biopsy (before embryo transfer) each blastocyst to ensure that the genetics (chromosomes) contained in each cell’s nuclear DNA were normal. This pre-implantation genetic screening (PGS) could thereby increase implantation rates and add a new level of safety, as well as reassurance that if the embryo were able to implant, subsequent miscarriage would be less common.
DNA sequencing of embryos without unpleasant tradeoffs
Early PGS techniques (particularly when done on 3-day old embryos) were associated with several drawbacks, including the risk of harming the embryo, occasional false-positive results that led to discarding usable embryos, or the need to forgo fresh embryo transfers due to the long waiting time required to get the DNA test result. Luckily, further developments have allowed us to render those risks insignificant. This is especially true because most embryologists now only biopsy the outermost shell of the blastocyst without touching the fetal component. Also, since some clinics are able to perform same-day PGS and get the DNA results back within 24 hours, there is no longer the need to unnecessarily freeze all the embryos while waiting for the PGS results. This is key because despite some unproven claims to the contrary, we believe that fresh embryos do better than frozen.
Getting the complete picture with simultaneous nuclear and mitochondrial DNA testing
The most current state-of-the-art fertility treatments take nuclear DNA PGS to the next step by evaluating the “other kind of DNA” contained in the embryonic cell’s cytoplasm (not the nucleus) – the mitochondrial DNA, which directs the ability of the embryo to perform critical functions like cell division and implantation. Therefore even if an embryo has normal nuclear DNA it is far less likely to continue to grow after the transfer and successfully implant if mitochondrial DNA is not at appropriate levels. This latest generation PGS offers a far more precise analysis of the potential of each embryo than traditional PGS, with no tradeoffs.
I am proud that CT Fertility is one of the few fertility clinics in the world that offers routine simultaneous nuclear and mitochondrial DNA testing as part of its PGS program. We believe that the technology is affording more of our clients an added level of reassurance, choice and control, and reaffirms our proven commitment to increase success without escalating costs.