Women who delay childbirth may face infertility by the time they are ready to get pregnant as a women’s fertility is strongly influenced by her age. Age-related decline in fertility is primarily from the decline in the quality and quantity of the eggs. As such, a reasonable strategy to preserve fertility in women who wish to delay childbirth is to freeze their eggs.
Egg freezing is an increasingly popular method to preserve fertility but one must carefully consider if it is the right time to undergo this procedure. If it is done too early in life, the preserved eggs may never be used or if done too late, it could be an ineffective procedure.
What are the factors affecting success rates using egg freezing?
Age +Number of Eggs Retrieved
The two most critical factors determining the probability of achieving a child using previously frozen eggs are the woman’s age at the time of egg collection and the total number of egg collected.
The number of eggs naturally decline as the women ages from approximately 200,000 eggs at the onset of puberty to around 1,000 eggs remaining at menopause. After the age of 37, the rate of decline accelerates rapidly.
As the number of eggs progressively decrease, the quality of the eggs also decline and eventually a minimum threshold is reached where pregnancy is no longer possible. It is estimated that after the age of 45, most of the eggs will have abnormal number of chromosomes.
What are the factors to consider for egg freezing?
Age + Estimated Time for Possible Use + Budget
When a woman decides to freeze her eggs, there are several factors she needs to consider. These include 1. the woman’s age at the time of egg freezing, 2. the intended wait time before pursuing pregnancy and 3. the cost-effectiveness of egg freezing.
Several studies found that reproductive aging is primarily related to the age of the egg and is not influenced very much by the age of the uterus. This means that the probability of pregnancy when using previously frozen eggs is determined primarily by the age of the woman when the eggs were collected rather than the age when she gets pregnant.
If egg freezing is undertaken too early, there is an increased chance that the woman will never be required to use the stored eggs to have children. The woman would have also been unnecessarily exposed to the financial burden and risks associated with ovary stimulation and egg collection.
If egg freezing is undertaken at an older age, the chances of pregnancy will be low due to the reduced number of collected eggs and the decreased quality of the eggs.
In a study by Mensen et al., his team found the highest probability of live birth when egg freezing was performed at the ages <34, and little benefit over no action was seen at the ages 25-30 years. If the only consideration is maximizing live birth rates at any cost, egg freezing should be performed before the age of 34 years. However, when attempts to conceive are delayed for a long period of time and cost-effectiveness is considered, egg freezing can be considered at the age of 37 years.
What is the maximum age for egg freezing?
The maximum age for attempting egg freezing may be as high as 45 years, but the success was limited to those patients producing >5 eggs in response to ovarian stimulation according to a study by Spandorfer et al. in 2007. In this study, patients older than 46 could also get pregnant, but none of these pregnancies resulted in a live birth child.
In some countries, there is the age-limit for IVF using donor eggs. In the Netherlands, the age is 45 years and in Belgium, the ages is 47 years.
Many questions for egg freezing may come from women aged 38-44. Would they benefit from egg freezing? Egg freezing from women at this age group will result in fewer live birth rates and would need to undergo multiple IVF cycles to potentially achieve pregnancy. Women in this age group need to be thoroughly counseled about the low probability of success and the time and resources required to undergo multiple cycles.
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Pellestor F, Andréo B, Arnal F, Humeau C, Demaille J. Maternal aging and chromosomal abnormalities: new data drawn from in vitro unfertilized human oocytes. Hum Genet. 2003;112(2):195.
Mesen TB, Mersereau JE, Kane JB, Steiner AZ. Optimal timing for elective egg freezing. Fertil Steril. 2015;103(6):1551-6.
Spandorfer SD, Bendikson K, Dragisic K, et al. Outcome of in vitro fertilization in women 45 years and older who use autologous oocytes. Fertil Steril. 2007;87:74.
Stoop D. Social oocyte freezing. Facts Views Vis Obgyn. 2010;2(1):31-4.