Egg Freezing (Oocyte Vitrification) vs Ovarian Tissue Cryopreservation

What is Egg Freezing? 

Egg Freezing, also known as Oocyte Cryopreservation, is a trendy and effective strategy of cryopreserving and storing the woman’s unfertilized oocytes designed for preserving female fertility and delaying pregnancy. 

Egg Freezing has multiple steps — fertility assessment, Controlled Ovarian Stimulation, follicular aspiration (Egg Retrieval), freezing (slow–freezing or flash–freezing) of unfertilized oocytes, and storage of the frozen oocytes in liquid nitrogen tanks in an embryology lab. 

Who is it for? 

• Single women wishing to delay the pregnancy for the future. 
• Heterosexual couples who are unsure of having the baby right now but desire to have the new addition to their family in the future. 
• Lesbian couples worrying about fertility and wanting to delay motherhood for the future. 

When to try it? 

• If you want to delay pregnancy and would like to be a genetic mom of your baby.
• If you have a diminished ovarian reserve and/or irregular cycle and don’t ovulate regularly.
• If you cannot continue an IVF cycle but you are already on the stimulation stage.
• If freezing embryos is banned by law in your country but Egg Freezing is allowed.
• If you undergo therapy that may lead to loss of ovarian function and early menopause.
• If you undergo surgery that may affect your fertility.

How long does the Egg Freezing cycle take?

Basically, Egg Freezing is the first half of IVF. It typically takes about 10–14 days and requires 8–11 days of administrating hormone injections to stimulate the ovaries to produce multiple eggs in one menstrual cycle followed up by several ultrasound scans and serum tests to check the progress. If the Controlled Ovarian Stimulation cycle is successful, Egg Retrieval and Egg Cryopreservation are performed.

Egg Freezing Success Rates

Oocyte Vitrification is a versatile flash–freezing technique that provides a higher thawing survival rate compared to conventional Slow Freezing (SF). The oocyte survival rate after Vitrification is up to 90% while after slow–freeze it is 40–70% maximum.

What are the other options to preserve female fertility?

Ovarian Tissue Cryopreservation is an experimental female Fertility Preservation technique that involves freezing and Storage of tissue from the ovarian cortex. Cryopreserving Ovarian Tissue requires a laparoscopic surgery in which an ovary or part of an ovary (the egg–producing portion of the ovary, called the ‘ovarian cortex’) is removed. Ovarian Tissue contains undeveloped oocytes and can be re–implanted later.

When to try it? 

In many cases, cancer therapy affects fertility leading to an irreversible reduction or loss of ovarian reserve. Cryopreservation of Ovarian Tissue with thawing and re–transplantation of tissue after the cancer is in remission is a great option to achieve a pregnancy in the future as ovarian grafts contain thousands of eggs, allowing for multiple attempts of Fertility Treatment cycles. 

One of the main advantages of Ovarian Tissue Cryopreservation over Egg Freezing is that it can be performed in one day, allowing cancer patients to start chemotherapy the next day. On the contrary, Egg Freezing usually requires several weeks of hormonal Treatments before the actual collection of eggs is performed. 

The success rate of this technique is hard to estimate because most fertility clinics perform Egg Freezing cycles and not each clinic has Ovarian Tissue Cryopreservation Protocols. The survival rate of Ovarian Tissue after thawing is between 84% and 90 % depending on the case, Cryopreservation and thawing Protocols. Follicular survival rate (after a single freezing–thawing) ranges from 70% to 80%. The live birth rate per Ovarian Tissue transplantation varies between 20% and 40%.