Oocyte Vitrification: Procedure, Risks and Considerations

As a component of assisted reproductive technology (ART), oocyte vitrification or cryopreservation has grown to become an important fertility preservation option for women since the first live birth in 1978 using this process. 

What is Oocyte Vitrification?

Oocyte vitrification is a process by which a woman’s fertility is preserved for a later use.  The technology helps with the embryo and egg freezing, making it desirable in several circumstances challenging the ethical, religious and legal concerns surrounding the process.

Explain the Oocyte Vitrification Process

The oocyte vitrification procedure involves the preservation of oocytes or cells in ovaries at sub-zero temperatures through a solidification process for a long period of time. For the purpose, the oocytes are treated with cryoprotective additives (CPAs) to prevent the formation of ice, which may cause cryodamage. Then, they are kept in liquid nitrogen at -196° C or -321° F.

Various studies related to the vitrification process show that the more the oocytes or eggs are mature, the more the process is successful. The eggs when used later should be injected by the sperm for the freezing hardens the shell of the egg, which makes it difficult for the sperm to break into it by itself for fertilization. Before injecting the sperm, the egg is thawed. Once the oocyte is fertilized, it is transferred to the woman’s uterus using a catheter, similar to that done in the in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment.

Types of Oocyte Freezing

When it comes to oocyte freezing, there are two types:

  • Slow Freezing: Under this technique, a slow cooling process is followed, where the oocyte cell is cooled at a decreasing temperature of .3°- 2° C per minute until it reaches -196° C. The biological process at this temperature ceases, and the egg cell is safely preserved for use when required. The slow freezing method is a lengthy process that takes about two hours, and for this reason, it is not used for cryopreservation these days.
  • Vitrification: On the contrary, vitrification helps cool the oocyte cells instantly to -196° C or -321° F, making them appear vitrified or glass-like. The process takes just a few minutes, which is important for quality frozen eggs. Vitrification has gained much prominence owing to being an economical, quick and efficient method of cryopreservation. 

The quick freezing causes no formation of ice crystals, which can damage the cell structures. Alternatively, it requires a lot of cryoprotective additives to assist in freezing the oocyte cells at a faster rate. The large amount of water inside the cell has posed problems to the safety of cells during slow freezing, in which more ice crystals form as the freezing time extends.    

What are the Potential Risks Associated with Oocyte Vitrification?

Despite its success, oocyte vitrification comes with some risks related to ovarian stimulation, as well as egg retrieval. There are not enough studies conducted, and as a result, there are hardly much data showing the effects of ovarian stimulation or egg retrieval. The medical risk of ovarian stimulation is mild ovarian hyperstimulation syndrome causing nausea, abdominal pain, fatigue, headaches and irritation. 

The other risk is causing abnormalities if the eggs are not properly frozen. Moreover, there is also the risks of congenital defects because of freezing and thawing, which may cause damage to the ovarian tissue. The women who use their frozen eggs to become pregnant are subject to risks associated with IVF. A few of them to mention are premature delivery, multiple pregnancy, babies with low birth-weight, gestational hypertension and cesarean section delivery.

The women who attempt to become pregnant at an advanced age are at a risk of preeclampsia, gestational diabetes, low birth weight, preterm delivery or cesarean delivery. The risk of causing them may vary based on the patient’s health status and age. 

Also, Read: Slow Freezing or Vitrification: Which Is the Best

Oocyte Vitrification – General Considerations

Recent studies related to oocyte vitrification have established clinical results comparable with the results attained through fresh cycles. Henceforth, it has been regarded an ‘emancipation for women’, who for different reasons may delay becoming a mother. With oocyte vitrification, women could make reproductive choices easily by deciding when and with whom they want to have children.

The increase in the demand for the frozen egg donation has led to oocyte vitrification. A number of women with age-related infertility are opting for oocyte donation as a better treatment option. The other requirements of this vitrification is for cancer patients, who consider oocyte cryopreservation as the best fertility option. Other than cancer, the women with medical conditions such as autoimmune diseases that need gonadotoxic treatment, endometriosis experiencing reduced ovarian post surgery, and genetic aberrations causing early menopause or subfertility.

There is hardly any doubt that oocyte vitrification is an established technology with several considerations. More research should be conducted as the number of patients and oocyte cryopreservation cycles increase. When this technique is proving beneficial to several patients, there needs a system to monitor its progress, purpose and success rates attained.

Also, Read: Vitrification Of Eggs