Mark P. Trolice, M.D., board certified reproductive endocrinology and infertility specialist and founder of The IVF Center says one of the most common questions asked by his patients is, “Should I freeze my eggs or my embryos?”

Today, both options are viable options, depending on the patient’s life situation and circumstances. However, many patients respond to this with surprise, thinking it is better to have embryos frozen.

Why do so many women feel this way? And what has led to this belief?

The Evolution of Egg and Embryo Freezing

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 1986. Since then, embryo cryopreservation technology has helped bring hundreds of thousands of babies into the world, with as high a health level 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 1980s, the slower freezing techniques employed at the time created a risk of ice crystals forming 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 genetic damage to the egg. Also, after thawing and being combined with sperm, the egg ran the risk of weak 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.

Freezing Your Eggs Vs. Your Embryos

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 or donor. 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. 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.

So why not simply advise these patients to freeze embryos, given the popularity and success rate of the procedure through decades of experience? The answer is because freezing embryos represents only one of two viable options. Reproductive endocrinology and infertility specialists have a responsibility to suggest egg freezing to married couples, especially if the couple has taken it for granted, or expects that they would be freezing their embryos.

The Dilemma of Discarding Unused Embryos

Many couples might not understand why egg freezing would still be in the conversation.

When a couple chooses to freeze their embryos, surplus embryos are frequently created, embryos that the couple may never make use of, if they succeed in reaching their desired family size.

Unused embryos can represent both an ethical dilemma and a financial burden. Some couples may feel very uncomfortable discarding unused embryos, donating them to other infertile patients, or even donating them to medical research. Others may feel obliged to implant unused frozen embryos even when they don’t want to have any more children. Frozen eggs or sperm cannot initiate a pregnancy on their own, so the decision to dispose of one or the other is significantly less distressing.

Also, storing unused embryos comes with a real, financial expense which can amount to between $400 – $1,000 annually.

In the case of a breakup, separation, or divorce, dealing with frozen embryos can potentially be more complicated than gamete freezing. Sperm and oocytes clearly are the property of the individual, but what about the legalities of the frozen embryos, which possess cells from both partners, and are legally recognized as joint property?

In the early stages of embryo freezing, couples undergo counseling and a consent process where the eventuality of separation is dealt with. Consent forms contain precise clauses in the event of separation, divorce, or the death of one or both partners.

However specific a consent form may be, the potential will always exist for an expensive, destructive, and lengthy legal battle should there be a belligerent split between parties.

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, especially should she meet someone later on in life, and wish to start a family with that person.

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.

What Should You Do?

Modern developments and advancements in oocyte freezing have literally leveled 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.