Assisted fertilization

Egg freezing: what is the procedure?

There has been a lot of talk about the announcement by Apple and Facebook that they have decided to pay their employees for the freezing of eggs for future pregnancy research. In this way the woman would be free to devote herself to her career when she is young (and her fertility is at its peak) postponing the pregnancy to a later period, when she may even find the right person to have children with.

Freezing is seen as a way to counter a “ticking biological clock”. Indeed, it is known that the older women get, the more likely their oocytes will have chromosomal abnormalities that increase the risk of miscarriage or make conception very difficult or impossible.

Egg freezing: why is it not a perfect solution?

Eggs contain a lot of water and when frozen, crystals can form which damage their structure. For this reason the freezing techniques of a decade ago have not been as successful as the current ones.

In the last 5 years a different technique has been used which freezes the eggs so quickly that the crystals do not have time to form. This technique is called vitrification and the eggs frozen in this way have a similar capacity to the “fresh” oocytes of a young woman to lead to conception.

The American Society for Reproductive Medicine (ASRM) has only declared this technique non-experimental since 2012.

According to the ASRM as things stand there is insufficient data to recommend that women freeze their eggs for the sole purpose of delaying pregnancy,

The risk is that the spread of this practice of delaying pregnancy to promote a career could give women false hope.

Women should be properly informed by the clinics they consult about age, oocyte cryopreservation success rates (in relation to natural conception), risks, costs and alternatives to this type of approach.

What does it mean for a woman to freeze eggs:

Freezing occurs in three main steps:

1) stimulation of the ovaries

2) oocyte retrieval

3) freezing of the egg cells obtained

During stimulation, women take hormone therapy that stimulates the ovaries to produce more eggs in one cycle. During this phase women have to go to the doctor several times within a couple of weeks to monitor the treatment (the risk is that of ovarian hyperstimulation)

In general, it takes about eight to 14 days of treatment before the oocytes can be retrieved.

Recovery is via an aspiration needle and is performed under sedation.

Once the oocytes have been retrieved, they are frozen to be used later with in vitro fertilization.

What are the chances of pregnancy with frozen eggs?

The chances increase the younger the woman is. So it is good to freeze eggs between the ages of 20 and 30.

But freezing the oocytes does not mean certainty of pregnancy .

As for the difference between the pregnancy rates of in vitro fertilization using fresh oocytes and frozen oocytes, according to a study that examined about 11,000 in vitro fertilization treatments that took place in 2013, the treatments were successful in 56% of cases with fresh oocytes, and in 47% the treatments with frozen oocytes.

The researchers found no obvious cause for frozen oocytes to be less likely to lead to pregnancy and hypothesized that the eggs lost quality during the freezing and thawing processes.

However, a limitation of the study is represented by the fact that the statistics are anonymous and therefore the ages of the donors are not known, which could greatly influence the result.

Surely further studies are needed and very probably the freezing and thawing technique needs to be further perfected.

Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.

Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.

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