BRIGHT IDEAS

How does the process of Egg/Embryo Freezing work? What is the difference between the two and how successful are each of these techniques?

Bright Idea provided by Dr. John Jain

Either eggs or embryos can be used to preserve fertility. In both processes, hormonal injections are given for approximately 10 days to induce the production of multiple eggs, which are then retrieved by passing a needle through the vagina directly into the ovary. The procedure is done under light anesthesia and is painless. Eggs are frozen within four hours, or fertilized with sperm to create embryos, which are then frozen the following day. Since eggs or embryos are frozen to -196°C, they do not change and can last for many years.

When pregnancy is desired, eggs are thawed, fertilized with sperm and transferred to the uterus as embryos; or if originally frozen as embryos, thawed and directly transferred to the uterus. Embryos are transferred to the uterus using a soft plastic tube placed through the cervix. A woman can conceive a pregnancy from her previously frozen eggs or embryos and carry a pregnancy well into her 50’s as long as she is healthy and her uterus undamaged by cancer treatment.

Fertility preservation options are determined by the type and stage of cancer, the required treatment, and the age of the woman. For instance, women diagnosed with estrogen-sensitive breast cancer can be treated with protocols that maintain estrogens in the normal physiologic range. In general, the entire egg or embryo freezing process takes 2-4 weeks to complete.

Embryo freezing is available for women with a partner, or those using donor sperm. Until recently, the pregnancy rate from frozen embryos, approximately 25%, was higher than the rate seen with frozen eggs. However, in experienced centers, pregnancy rates of 30-40% are being reported from frozen eggs, thus giving women two viable options for fertility preservation.

The in-vitro fertilization processes used for egg and embryo freezing have been available for many years and are considered safe. However, since there are only 500-600 babies born to date from egg freezing, the technique is still considered experimental. For this reason, women should work with centers specializing in egg freezing who can properly inform them of the risks and benefits involved.

Ovarian tissue freezing is another experimental method of fertility preservation. In this technique, ovarian cortex (the outer shell of the ovary) is surgically removed with the aid of a laparoscope and frozen for future use. To date only 5 babies have been born from transplanted, frozen ovarian tissue. Concern for reintroduction of tumor cells limits the widespread use of this technique.

Selected Bibliography
Jain JK. One patient’s journey (fertility preservation). Women and Cancer: Summer 2008:92-93

Jain JK, Paulson RJ. Oocyte cryopreservation. Fertil Steril 2006;86(Suppl 3): 1037-46

Jain JK, Francis MM, Marsh EM, McConnell G, Quinn P, Chung K, Paulson RJ. Oocyte cryopreservation: A promising strategy for circumventing the age-related decline in human fertility. 54th Annual Meeting of the Pacific Coast Reproductive Society, April 26-30, 2006, Indian Wells, California. (Winner of General Program Prize Research Paper)

Jain JK, Francis MM, Bayrak A, Quinn P, Paulson RJ. Pregnancy outcome after cryopreservation of all oocytes from a single ovulatory cohort: A prospective clinical trial. Fertil Steril 2005;84(Suppl 1):S350-1.

Jain JK, Fritz MA. Controversies in OB/GYN. Is egg freezing ready for primetime. Contemporary OB/GYN 2007:86-95

Paulson RJ, Boostanfar R, Saadat P, Mor E, Tourgeman DE, Slater CC, Francis MM, Jain JK. Pregnancy in the sixth decade of life: Obstetric outcomes in women of advanced reproductive age. JAMA 2002;288:2320-3.