The importance of the embryologist’s role in embryo freezing, also called cryopreservation, has grown with the rise in pre-implantation genetic testing and “freeze-all” strategies. Embryo cryopreservation and maintenance is considered to be a standalone sub-discipline of reproductive medicine. Embryo cryopreservation allows women undergoing IVF to have just ONE cycle, but continue to have embryos to use in the future. It helps to reduce the risk of Ovarian Hyperstimulation Syndrome (OHS), and allows for the endometrium to fully recover after ovarian stimulation.
The idea of maintaining the viability of living reproductive cells and tissues of various species and humans for long-term storage has been around for almost 50 years. Dr. Alan Trounson and Linda Mohr achieved the first human pregnancy from a frozen (8 cell) embryo in 1983 and the first live birth, baby Zoe, in 1984. In 2017, Emma Wren Gibson was born from an embryo that had been frozen for nearly 25 years – possibly the longest gap between conception and birth since IVF began.
Overall, embryo cryopreservation has decreased the number of fresh embryo transfers performed, and maximized the effectiveness of IVF cycles.
Through efforts to constantly improve cryopreservation techniques, we are now able to preserve cells and tissues through a process called vitrification – transforming cells from a liquid state directly to a glass like state. This is done by replacing all the water in cells (dehydration) with a cryopreservation agent, and then by cooling the embryos to extremely low temperatures, such as −195.79°C (the boiling point of the liquid nitrogen). Cooling down biological objects to such degrees prevents any biological activity, including all the biochemical reactions involved in cell death!
When cryopreservation methods fail, dreams and families are lost. Several high profile cases of liquid nitrogen storage failures, as well as the selection and transfer of the “wrong” embryo have been nightmare scenarios for the IVF industry. They highlight the embryologist’s important role in cryopreserving and storing embryos. Some of the roles and responsibilities of embryologists are: