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Vitrification of oocytes: how is the freezing of oocytes in France?


Authorized in France since 2011, oocyte vitrification allows women to resort to assisted reproduction later in order to have a child. Since the law on bioethics published on August 2, 2021 in the Official Journal, the freezing of oocytes is possible without medical reason.

What is an oocyte?

Definition of the oocyte

The oocyte is the female reproductive cell, the equivalent of the sperm in women. Oocytes are stored in the ovaries from birth. Every month, on the 14th day of the menstrual cycle on average, an oocyte is released from one of the two ovaries (the left or the right) and descends into the corresponding fallopian tube to be fertilized by a sperm. The oocyte becomes an ovum if it is fertilized by a sperm. Fertilization takes place in the fallopian tube.

The function of the oocyte

The release of an oocyte occurs every month. A woman’s stock of oocytes determined at birth therefore decreases over the years. The quality of these cells also decreases with age. It is estimated that after 35 years, the oocytes are of poorer quality, the chances of conceiving after this age are reduced. The decline in ovarian reserve is therefore a natural phenomenon against which we cannot fight. Today, only the vitrification of the oocytes makes it possible to have access to ART later to try to get pregnant with his own gametes at a more or less advanced age.

What is oocyte vitrification?

Vitrification of oocytes is a technique which involves immersing the oocytes very quickly in liquid nitrogen at -196 ° C. This allows almost instantaneous freezing of the oocytes which guarantees the integrity of their cellular structures. In other words, vitrification makes it possible not to alter the quality of the oocyte and therefore not to reduce its capacity to be fertilized and to form an embryo after thawing.

Before the onset of vitrification, oocytes were stored using slow freezing techniques which could lead to the appearance of intracellular crystals that were detrimental to their quality.

What are the different stages of oocyte vitrification?

Oocyte vitrification concerns women who wish to delay their plans to have a baby and those who wish to donate their oocytes to help women who cannot become pregnant with their own gametes. A decree published on September 28, 2021 indicates that the collection of oocytes can be carried out in women from their 29th birthday and until their 37th birthday to benefit from the self-preservation of their gametes for the subsequent realization of medically assisted procreation.

Step 1: first consultation and medical check-up

The patient should first see a doctor to assess her chances of success and learn about the risks of ovarian stimulation and egg retrieval. A health check-up is also necessary to check the fertility of the patient and the feasibility of self-preservation of the oocytes. Ovarian function is assessed in particular through blood tests, ultrasound and gynecological examinations.

Step 2: ovarian stimulation

To promote the production and maturation of several oocytes, ovarian stimulation is essential before removing the oocytes. It consists of daily subcutaneous injections of hormones for 10 to 12 days given either by a nurse or by the patient / donor herself. During stimulation, several ovarian blood tests and / or ultrasounds are performed to adapt the treatment to the ovarian response.

Step 3: collecting the oocytes

The oocytes are collected in the hospital under short-term general anesthesia, locoregional anesthesia or simple anesthesia. The sample takes place over a day and is done 35 to 36 hours after the last injection of hormones. It is done vaginally under ultrasound and lasts about 10 minutes. The patient should then remain under medical supervision and rest for approximately 3 hours.

Step 4: freezing the oocytes

Once collected, the oocytes, in contact with high concentration cryoprotectants, are immersed directly in liquid nitrogen at – 196 ° C. Cryoprotectants are substances added before freezing to prevent the formation of crystals inside the oocytes and thus prevent damage linked to the rapid drop in temperature.

How long are the oocytes kept?

The bioethics law of August 2, 2021 recalls that women who have self-preserved their oocytes must each year inform the AMP (Medical Aid for Procreation) center where they are kept of the action to be taken:

  • keep them;
  • use them for an MPA;
  • give them to people awaiting donation of gametes;
  • donate them for scientific research;
  • end their retention.

Women who have self-stored their oocytes can dispose of them until the age of 44 (under 45).

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