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.
That all changed in 2012 when fertility specialists introduced a new flash-freeze process called vitrification, which combined with ICSI sperm injection, led to normal rates of fertilization. As a result, fertilization and pregnancy rates are as high for frozen eggs as with fresh eggs.
Embryo Freezing: A deeper insight
During an IVF cycle, many embryos are created. Usually, just one or two embryos are transferred back into the womb of the female patient and the supernumerary embryos are frozen or cryopreserved. Embryo freezing is the leading method of fertility preservation. In the past, embryos were frozen using a slow process, but that has changed in recent years.
Egg freezing processes were initially developed to allow women (single or married) the luxury that men have had for years: the ability to preserve their fertility without a partner. The best example is that of a woman with cancer who wishes to safeguard her fertility before undergoing chemotherapy treatment that could be potentially sterilizing.
This benefit now extends to women who are considering egg freezing for social or personal reasons, such as delaying starting a family to focus on their careers. Freezing eggs means women can avoid the adverse reproductive impacts of advancing age when child rearing is deferred to the future.
However, what is also another trend is couples in their late 30’s or early 40’s who are ready to start families, but who would like to have more than one child can also benefit from the freezing of female oocytes.
Concerns related to Embryo Freezing
- One of the concerns being discussed is how to dispose of embryos that are not used, and as more people seek out IVF and embryo freezing, there are more issues that arise as a result of unforeseen circumstances. Frozen eggs are not yet fertilized and, therefore, generally considered to still be under the ownership of the woman from whom they were harvested.
- Embryos are created from fertilizing sperm and an egg. If a couple created the embryo and if the relationship comes to an end, then the case could end up in court to decide ownership or a fair resolution.
- Whether you are a hopeful future single parent or a couple, there could be both ethical and religious issues to consider before starting the process.
Flexibility in Future Family Planning
- Single women wishing to preserve their fertility through egg freezing often consider freezing embryos using donor sperm instead, or freezing a combination of both eggs and embryos. If a woman is 100% sure she would like to be a single parent using donor sperm, then it naturally follows that she would elect to freeze her embryos.
- However, no matter how certain one is at any given point in time, as with all things in life, one’s personal circumstances can change. Creating embryos with donor sperm could effectively lock a patient into using that option. If she were to especially meet someone later on in life, and wishes to start a family with that person, then her chances of having a genetic child of her own would be much higher if she had frozen oocytes (eggs) instead of embryos with door sperm.
- No one can perfectly predict the number of embryos that may result from frozen eggs. Nevertheless, it is important that fertility specialists provide medically documented statistics about the integrity and health of eggs after thawing, and expected fertilization rates and pregnancy rates per embryo transfer.
The calculation and consultation should be adapted to each woman’s unique situation, including her age, general health, lifestyle, and medical history.
Modern developments and advancements in oocyte freezing have literally levelled the playing field between women and men vis à vis preserving and expanding their fertility choices (removing a woman’s eggs is, of course, more complicated than getting a sperm sample!).
At the end of the day, fully-informed patients and couples can make the best decisions and choose the optimal course of action for their reproductive and life goals.
Have more questions about freezing eggs vs. freezing embryos? We’re here to help. Write to us at firstname.lastname@example.org to book an appointment.