Fertility preservation is an emerging area of reproductive medicine that empowers women to make well-informed decisions regarding their reproductive options. In October 2012 The American Society for Reproductive Medicine (ASRM) published practice guidelines that removed the experimental label from oocyte cryopreservation. To date, there have been over 2,500 live births achieved from oocyte cryopreservation without an increase in pregnancy complications or congenital anomalies.

It is commonly known that as age increases, the chance of pregnancy decreases. At the same time, the rate of spontaneous miscarriage and the chance of having a child with a chromosomal abnormality increases with increasing age. The monthly chance of achieving pregnancy gradually but significantly begins to decline at age 32 and decreases more rapidly after age 37. Other modifiable factors that are known to impact a patient’s fertility include tobacco use and obesity. These realities are driving many women to inquire about their ovarian reserve and consider oocyte vitrification as a means to extend one’s reproductive window.

We recommend women who are considering egg freezing, to undergo ovarian reserve testing. Ideally, women are off hormone contraception for at least a month prior to testing. We use this opportunity to also conduct preconception testing such as viral titers and genetic carrier testing. We view egg freezing as the ultimate in preconception and another opportunity to educate women regarding the value of this testing.

Interesting, studies following women that obtained ovarian reserve markers who had been trying less than 3 months, or in the context of a desire to learn about “reproductive potential”, did not find a relationship between abnormal ovarian reserve markers and fertility. In other words, ovarian reserve markers help to determine response to gonadotropins and egg yield for patients considering egg freezing but can’t predict reproductive potential in women who are not infertile.

Although the first successful birth from egg freezing occurred in 1986 by Chen et al, it wasn’t until 2012/2013 that ASRM/ACOG, removed the experimental label from egg freezing. Egg freezing was initially performed using a slow free technology, the use of vitrification has greatly improved success. 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 cells. At FCI, we have been using vitrification technology for embryos for 13 years with 95% survival rates upon warming. Oocytes that are frozen using vitrification technology have yielded similar survival rates.

Studies have suggested for women less than 38 pregnancy success from vitrified eggs is similar to fresh. For women older than 38, although embryo freezing is more successful it requires either a partner or a sperm donor. The approach of egg freezing has been to create a sufficient number of eggs for women of varying ages to allow for success. For instance, women less than 35 years old likely need 12-15 mature eggs to have an 80% chance of a SINGLE live born from those eggs. Women who are 38 years old require 25-30 and women who are 40 years old require 50 mature eggs for similar success. Questions that still remain is what is a reasonable number if a woman desires many children? How do we best counsel women with low yields of oocytes from an egg freezing cycle regarding natural conception?

Data looking at children created from egg vitrification has been reassuring. There has not been shown an increase in aneuploidy or birth defects from these children. Although initial data is reassuring, a worldwide database would be ideal. The literature has demonstrated comparable pregnancy rates between fresh and frozen oocytes. Cobo and Diaz published a meta-analysis in Fertility and Sterility, August 2011, and combined data from the use of 22741 frozen oocytes. Pregnancy rates in the vitrified oocyte group were 49.1% compared to 48.3% in the fresh group. Our very own lab at FCI has demonstrated similar success rates with vitrification technology. At FCI, we have been doing egg freezing since 2004, initially for cancer patients. We have vitrified 10,845 oocytes to date from 921 patients with a mean age of 35.8 years. To date, we have warmed 720 oocytes with a clinical pregnancy rate of 45-48%.

 

Suggested readings:

Steiner et al. Associations between biomarkers of ovarian reserve and infertility among older women of reproductive age. JAMA. 2017:318(14):1367-76.

Goldman et al. Predicting the likelihood of live birth for elective oocyte cryopreservation: a counseling tool for physicians and patients Hum Reprod 2017 32(4): 853-859