Egg Freezing 2015 – An Update
Since the late 1990s we have been able to freeze human eggs successfully. It is imperative that we continue to add to our knowledge base concerning egg freezing and answer some of the difficult questions that are posed by our technical ability to provide this service. This requires that we carefully monitor outcomes in those patients who have frozen eggs and have utilized these eggs to achieve pregnancy. Our understanding of egg freezing outcomes is somewhat limited at this time primarily because many women who have frozen their eggs have not yet used them. Babies born after use of frozen eggs are not yet old enough to have been studied properly.
As public awareness and utilization of egg freezing increases, we must be prepared to answer questions about this relatively new treatment option. Some of the important questions that arise include the following:
1) Who should consider egg freezing?
A. Egg freezing should be offered to any woman who desires children in the future and is facing surgical, radiation, or chemotherapy which may adversely impact future ovarian function. It should also be considered by any woman who must delay childbearing because of prolonged education requirements, career choices, or because she has not found a suitable partner.
Many have drawn a distinction between “medical egg freezing” and “social egg freezing”, with medical egg freezing being done when there is an immediate need to preserve fertility such as before cancer therapy. Social egg freezing is the term used to describe egg freezing that is done when there is a desire to delay parenthood so that educational, professional, or other goals may be met. Most people would consider medical freezing to be acceptable and worthy of societal support, possibly even financial coverage. Others might consider social freezing to be unacceptable and unworthy of coverage.
2) What is the best age for egg freezing?
A. As might be expected, freezing eggs at a younger age is preferable to freezing later in life. Available data suggest that thawing 6 eggs from women at the ages listed below will result in a live birth at the following rates:
Age 25 – 31%
Age 30 – 24%
Age 35 – 18%
Age 40 – 13%
Given this data, utilization of 24 frozen eggs from a 25 year old woman would lead to a live birth in about 77% of patients. Obtaining this number of eggs would likely require two egg retrievals. The concerns about freezing eggs at too early an age center on the strong possibility that these eggs might never be needed, and therefore the efforts and expense of freezing would be wasted. On the other hand, freezing eggs late (age 40 or older), presents difficulties because obtaining adequate numbers of eggs from this group is more difficult, leading to an increased number of procedures needed to obtain a satisfactory number of eggs to achieve a live birth. While 24 eggs in 40 year old patients would lead to a live birth rate of approximately 42%, obtaining this quantity of eggs in these older patients might require 5 or 6 egg retrievals.
Given the discussion above, it seems that at the present time the ideal age to freeze eggs is 30-35. In this group, a 60% live birth rate could be achieved with 24 eggs.
3) Is egg freezing safe?
A. There are 2 important factors that limit our ability to evaluate the safety of egg freezing. First, many women who have elected to freeze their eggs have not yet used them. Second, most of the babies born following the use of cryopreserved eggs have not reached the ages at which safety can be fully evaluated. Chromosomal studies comparing embryos created from cryopreserved eggs vs. controls have shown no difference in the incidence of chromosomal abnormalities. One fairly large study published in 2013 in Fertility and Sterility did show a significant increase in miscarriage rates among pregnancies conceived from frozen eggs compared with non-frozen eggs.
4) How much does it cost to freeze eggs?
There are a number of steps involved in calculating the total cost of egg freezing including:
AT A LATER DATE
embryo replacement in the uterus
The“immediate” costs for egg freezing will vary from clinic to clinic but should generally fall within a range of $7,000 - $12,000, for each egg retrieval and freezing. The “later date” costs will likely be in the $3000 - $5000 range in today’s dollars.
5) Is there a best method of egg freezing?
Egg freezing has proven to be challenging because of ice crystal formation on the interior of cells as the cells are cooled. Additional problems included hardening of the outer membrane surrounding the egg as a result of freezing, and damage to the delicate meiotic spindles within the egg from ice crystals. Cryoprotectants have long been used to protect cells from damage due to freezing. However, these agents have toxicities at high concentrations. In 1997, there were reports of 80% post-thaw survival through the use of propanediol as the cryoprotectant and utilization of direct intracytoplasmic sperm injection (ICSI) to achieve fertilization.
Slow Freezing or Vitrification
Early work with egg freezing was done with “slow freezing” which involves slow reduction in temperature while the concentration of cryoprotectants is increased. Studies looking at fertilization rates of thawed eggs following slow freezing have shown a significant reduction in fertilization, clinical pregnancy rates, and live births compared with fresh eggs.
Vitrification involves rapid cooling of cells to extremely low temperatures. During this process cells are exposed to very high concentrations of cryoprotectants. Because this process is so rapid, ice crystals do not have a chance to form. Studies have demonstrated higher rates of fertilization, cleavage, and clinical pregnancy rates for vitrified eggs compared with eggs that were frozen slowly. A recent comprehensive review of available data indicates that vitrified/thawed eggs result in similar fertilization and pregnancy rates when compared with IVF/ICSI with fresh eggs.
Advances in egg freezing offer options to women that have never before been available. As providers of reproductive care it is our responsibility to generate greater public awareness of this option and to be leaders in helping our patients gain access to egg freezing. Health insurance coverage for egg freezing is not yet a reality and will need to be addressed in the future. The decision to cover egg freezing by insurers will be based on many factors including social benefits, chances for success, and costs.
Source: Abusief, ME, Adamson, DG. Fertility Update, OBG Management, Feb