Oocyte preservation—more commonly known as egg freezing—is now such a routine and successful protocol that it’s sometimes hard to remember that the world’s first birth from a frozen egg occurred less than 30 years ago.
Cryopreservation of sperm has been a mainstay of reproductive technology since the early 1950’s. But eggs are more delicate than sperm. As the largest cell in the human body, they have a very high water content—putting them at risk for ice crystal formation. Freezing eggs is a complex procedure—made easier and more successful, to be sure, by recent advances such as “vitrification”, the flash freezing of eggs, which greatly reduces the failure rate associated with older, slow-freezing technologies.
The earliest experiments with using cryopreservation of eggs for fertility were done on mice during the 1960’s. By 1972 science had recorded the first success birth of a mammal—a mouse again– from a frozen embryo. It was only a matter of time before the techniques were refined for human eggs and embryos.
The world’s first successful human pregnancy using a previously frozen oocyte was reported by an Australian, Dr. Christopher Chen in 1986. Since then, thousands of babies have been born from frozen eggs. And as many as 500,000 children have been born using slow-freeze cryopreservation techniques. The addition of vitrification to the egg freezing arsenal promises many more successful pregnancies and births.
Egg freezing was called “experimental” until 2012 when the designation was finally lifted. But, as you can see, it’s not new science. Advances in cryoprotectants and the techniques and technology necessary for faster freezing will continue to evolve. We’ve come a long way in less than 30 years. The past is interesting. The future looks promising.