Fertility clinics have successfully frozen embryos for more than 30 years, since an infant girl named Zoe became the first child born from a frozen embryo in Melbourne, Australia in 1984. Since then, embryo cryopreservation technology has helped bring hundreds of thousands of babies into the world, with as high a health level and live birth rates as in vitro fertilization (IVF) with fresh embryos.
Egg freezing, on the other hand, has had to overcome some particular challenges to get where it is today. When egg freezing began in the 1980’s, the slower freezing techniques employed at the time created a risk of ice crystals formation during the freezing process. The human egg is not only the biggest cell in the body, but it also possesses a large amount of water; and ice crystals that form during the freezing process can cause cryo damage to the egg. Also, after thawing and being combined with sperm, the egg ran the risk of poor fertilization outcomes due to the outer shell of the egg (called the zona) having hardened during freezing.