By Eve Feinberg, M.D.
As a fertility specialist, I see a wide variety of patients. In addition to infertile couples trying to achieve pregnancy, I see many single women interested in options for preserving fertility. With cancer therapies becoming even more successful in achieving cures, I also see a number of women with newly diagnosed cancer who are interested in fertility preservation options.
So…what are the different available options?
1) Oocyte vitrification “egg freezing”
Vitrification is a freezing method that encases a cell in a glass like (vitreo = glass in Latin) ball of ice. Vitrification does not cause ice crystal formation and therefore causes less damage to a cell. The egg is the largest single cell in the female body and the DNA contained inside the egg is especially sensitive to ice crystal formation. With the advent of vitrification technology, oocyte vitrification has rapidly advanced. Recent studies have shown that pregnancy rates from oocyte vitrification are almost comparable to pregnancy rates from traditional in-vitro fertilization (IVF).
The eggs are harvested in the same manner as if a woman was undergoing IVF. Injectable hormones are self-administered over a period of 1-2 weeks to stimulate the ovaries to produce eggs. During this time, a woman’s ovaries are monitored with almost daily transvaginal ultrasounds and blood estrogen levels. The ovaries respond to the medication by developing large follicles. Follicles are fluid filled spaces that contain an egg. When the follicles measure 16-20mm in size, another hormone is given to allow the egg to fully mature. 36-38 hours after this last shot is administered, the woman is put to sleep and the eggs are extracted from the ovaries using a transvaginal ultrasound with a needle attached. The needle goes through the vagina and into the ovary to remove the eggs. The eggs are passed off to an embryologist for inspection and rapid vitrification. The egg retrieval procedure only takes 15-20 minutes. Vitrified eggs can remain in storage for as little as a few hours or as long as a few years. When a woman is interested in using her eggs, they would be warmed and then inseminated with sperm. The day after insemination, the embryologist would check to see if the egg fertilized and then would allow the fertilized egg (now considered an embryo) to grow and develop in the laboratory for 3-5 days. The embryo or embryos would then be transferred back to the woman’s uterus. Nine to 11 days later, if pregnant, a blood pregnancy test would be positive.
Oocyte vitrification is an emerging option for fertility preservation in single women who wish to delay childbearing and in single women faced with a cancer diagnosis. For women with breast cancer, there are medications that can be given while stimulation is occurring to prevent estrogen levels from getting too high. Studies have demonstrated the safety of oocyte vitrification in cancer patients and have not shown earlier recurrence or worsening of survival rates. Another novel use of oocyte vitrification is in the arena of oocyte donation. Currently, nearly all oocyte donation cycles are fresh donations from an egg donor undergoing stimulation. It is realistic that in the next few years that egg donors may be able to undergo ovarian stimulation and eggs frozen well in advance of the time that they are going to be used. It is likely that egg banks will be established and prove a viable option for couples . It is also likely that women in their 20’s and early 30’s will be able to successfully bank eggs for the future to intentionally delay childbearing.
2) Embryo vitrification
Embryo vitrification is the best available technology for fertility preservation because. A vitrified embryo can remain in storage for 5-10 years and has an incredibly high likelihood of survival and pregnancy. For cancer patients who are married or are in a stable long-term relationship, embryo vitrification is the treatment of choice. Embryo vitrification is also a viable technique for single women who desire children, but wish to delay childbearing. A sperm source is needed and could be obtained from an anonymous sperm donor (most common) or from a known sperm donor (less common). Anonymous donor sperm is readily available through a sperm bank. A woman’s eggs are harvested in the same manner as for oocyte vitrification. Rather than the oocyte being passed off to the embryologist and vitrified, the oocyte is passed off to the embryologist and fertilized with sperm. The embryo grows in the laboratory until it is suitable for vitrification. The point in time at which vitrification happens differs by lab. Some labs choose to vitrify at the pronuclear stage, some at the day 3 stage and others at the blastocyst stage (days 5 or 6).
Embryo vitrification has the highest success rate of any treatment, but requires a sperm source. For a woman who prefers to leave her options open with regard to sperm source, other methods of fertility preservation may be more desirable
3) Ovarian cryopreservation
This technique requires removal of an ovary and freezing strips of the ovary for the future. These ovarian strips would later be thawed and re-implanted into a woman so that fertility could be restored. Of all technologies, this is considered to be the most experimental and has the fewest numbers of children born to date. There have, however, been a number of case reports of healthy children born from ovarian cryopreservation. This is a good option for a cancer patient who does not have the time to undergo ovarian stimulation for either oocyte or embryo vitrification.
Fertility preservation is an emerging area of reproductive endocrinology that empowers women to make fertility sparing choices when faced with a cancer diagnosis or when faced with the aging process without the immediate desire to become pregnant.