OOCYTE CRYOPRESERVATION

OOCYTE CRYOPRESERVATION

 

in this modern society where women are more empowered and equality has become the norm, many organizations are run by able women. With more responsibilities over the shoulders, modern women are more likely to slow down their plans for marriage and have a child. However, according to several studies, women at age 35 or older have less chance to get pregnant and greater risk of infertility, as age is an important factor for fertility. The older a woman gets, the fewer eggs she has in her ovarian reserve and less competent the oocytes are. (Cimadomo et al., 2018) For these reasons, oocyte cryopreservation technology has become one of the readily available methods to ensure healthy eggs saved for later.

 

Oocyte Cryopreservation

Cryopreservation involves the preservation of cells and tissues for extended periods of time at sub-zero temperatures. Cryoprotective additives (CPAs) are used in order to reduce cryodamage by preventing ice formation. The eggs are stored in -196°C liquid nitrogen. There are two basic techniques generally used in the cryopreservation:

1. Slow freezing Oocytes are cooled at a slow rate of 0.3–0.5°C/minute controlled by computer.

2. Vitrification A newly developed technique with fast cooling rates of 15,000-30,000 °C/minute using more concentrate CPAs to create a glass-like stage and prevent ice formation which would damage the egg cells.

 

Vitrification is now more widely used than slow freezing due to its convenience and less time-consumption. The technique mitigates cryodamage and contributes to a higher survival rate after the thawing. The success for clinical pregnancy rate (CPR) is virtually the same as fresh oocytes. (Argyle et al., 2016) However, the success rate after thawing is based on the age of the eggs. Eggs at age up to 35 years old have a 48.6% chance of success. Such chance is lower with higher ager. At age 41-43, the success rate drops to only 22.2%.

 

Women Who Should Use Oocyte Cryopreservation

1. Those who are at risk of losing their ovary function due to various medical issues such as cancer, radiation, or chemotherapy treatment

2. Those with ovarian disorder such as tumor or cyst

3. Cryopreservation can be helpful to store eggs in an infertility treatment program where sperms cannot be collected from the man on the same date of egg collection.

4. Preserving the oocytes will bypass any legal or ethical problems that are associated with frozen embryos.

5. Those who wish to donate to the egg bank

6. Those with early menopause history in the family

7. Those who plan to have a child in the future, called ‘social egg freezing’

Social egg freezing is becoming more and more popular nowadays as women tend to delay their motherhood, for example to focus on their career or education. Large companies like Facebook, Google, and Apple encourage their female employees to use oocyte cryopreservation so they can fully focus on their job without having to rush pregnancy.

 

Preparation and Oocyte Collection

The basic preparations for people who wish to use oocyte cryopreservation are similar to normal IVF. First, health checkup is conducted by a specialized physician. The client will be given daily oocyte stimulant and monitored. Once the oocytes are at the desirable size, the client will be given HCG hormone that stimulate  the oocytes to become mature. 36 hours afterwards, the oocytes will be collected through vagina. The embryologist will select only healthy, mature oocyte to freeze.

 

Success Rate

The success rate of oocyte cryopreservation used in IVF or Intracytoplasmic Sperm Injection is now similar to those achieved with fresh oocytes. There is also no evidence that children bornwith a frozen oocyte show more signs of abnormalities than IVF or ICSI. (Argyle et al., 2016; Crawford et al., 2013) A client at Jetanin has had her 6 oocytes stored with vitrificationfor almost 10 years, starting in 2009 (age 36 at the time). Later in 2018 (age 45), her oocytes were thawed with 100% survival rate and 83% fertility rate. After 5 days, the 4 of the embryos developed into blastocysts, or 80% of the embryos. There were 2 embryos transferred and the client achieved pregnancy with 2 more embryos kept frozen for the future in case she wants to have another child.

 

Oocyte cryopreservation is a great option for women to preserve fertility in anticipation of age-related fertility decline which may lead to abnormalities in the child.


Written by
Kanokwan Kamquan,
Medical Technician, Embryo Laboratory
Jetanin Hospital

JETANIN Journal Vol.10 No.3

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