Technicality Level: Moderate
Advanced infertility treatments are one of the fastest developing areas in medicine. Improved, current technologies, and the emergence of new technologies is a common encounter. The way assisted reproduction was approached but only two years ago are very different from what is being considered state-of-the-art today.
Time-lapse photography now allows us to place a microscope inside of the incubator instead of frequently taking the embryos out of the incubator to the microscope for evaluation. Low-light, low intensity photographs are taken minutes apart, creating a video of embryo development. The end result is that the embryos can be cultured without interruption for 6 days, reducing the exposure and resultant stress to the embryos while, simultaneously, embryologists gain more information on embryo development than ever before. Embryo developmental events such as asynchronized divisions, slower-than-normal cell divisions, division timings and abnormal cell divisions can be readily identified. Pregnancy rates are significantly improved due to the lower stress on the embryos and the deselection of compromised embryos.
New vitrification techniques allows for the snap-freezing of embryos, using a special vitrification solution, not much different from radiator fluid in car engines. Previously, one had to freeze an embryo over a period of hours, mitigating cryoprotectant exposure and ice crystal formation. Only good-quality embryos of certain developmental stages could be frozen and, we were happy when 80% of embryos survived. With vitrification, there is no ice crystal formation (glass formation instead), and, any quality- and stage embryo can be cryopreserved. Most importantly, the survival rate approaches 100%. With a close to 100% survival rate, it now becomes feasible to transfer one embryo at a time, reliably preserve biopsied embryos during the process of preimplantation genetic screening (PGS) and preferably perform frozen embryo transfers in a carefully prepared uterus instead of transferring embryos fresh into a supraphysiological-hormone-exposed uterus. One very exciting development is that vitrification, for the first time, allows for the routine cryopreservation of oocytes (eggs) – this was not possible only a few years ago. Oocyte cryopreservation is a new and essential tool to offer fertility preservation to cancer patients, banking of fertility potential for aging professional women or increasing the options for donor eggs.
PGS is a technique where placental (trophoblast) cells are sampled from a blastocyst-stage embryo and then send to a genetics referral laboratory for determination of the chromosomal count in the embryo. The most common cause of an unsuccessful pregnancy (natural effort or with assistance) is an abnormal number of chromosomes in the embryo (aneuploidy). After biopsy or sampling, the blastocysts are vitrified and safely kept in storage for the two weeks or so that it takes to receive the results. Once we have results, we can warm or thaw only the normal and uncompromised embryos. Transferring only a confirmed, chromosomally normal embryo, ensures equivalent live birth rates for all patients, regardless of maternal age. This is in contrast to the typical age-related decline in live-birth rates when transferring unscreened embryos. Furthermore, live birth rates are increased and miscarriages are reduced for women 35 years or older.
With the advent of vitrification, and 100% survival rates, it is now possible to transfer a single embryo for most patients in replacement cycles after cryopreservation, instead of in fresh hyperstimulated cycles. This allows for the optimization of the implantation lining of the uterus with a 10-20% increase in live birth rates.
Routinely culturing embryos to the blastocyst stage with the use of low-oxygen culture, time-lapse culture systems and, improved culture media and platforms, now allow for the selection of embryos based on the quality and presence of the baby part (inner cell mass). We will only cryopreserve proven and likely viable embryos and have access to trophoblast cells for biopsy and PGS.
These new developments have significantly increased success rates. Infertile patients now have access to ever growing and improving technologies which, ultimately, get them pregnant faster and allow us to help a broader spectrum of infertile patients, previously not possible.