How does embryo freezing (cryopreservation) work?

Treatment and Monitoring

Why can we not always freeze the embryos left over from a fresh cycle?

We can freeze embryos in the majority of fresh cycles carried out.
We place the left over embryos in a culture medium to monitor their evolution and biologists will determine whether they can be frozen or not.
The freezing criteria are different to the criteria to evaluate the transfer of fresh embryos: they must meet much more specific requirements as the freezing and thawing processes are processes which are aggressive to the embryos.
If we froze all the leftover embryos, the cancellation rates of a transfer after thawing would be very high, so we do not freeze all the embryos that are left in the laboratory after a fresh transfer. In spite of these requirements, there is a 22% cancellation rate for cryotransfer after the thawing and re-adaptation in a culture medium of the embryos.

Is there any connection between the cryopreservation of embryos and pregnancies occurring from the fresh embryos transferred from the same cycle?

It is more difficult for the embryos to develop in the laboratory than in the mother’s uterus. According to studies carried out, there is no logical connexion between embryos being frozen and the pregnancy rate from fresh embryos. Therefore, if we cannot freeze a part of the leftover embryos does not mean you are any less likely to become pregnant or vice versa.

How long can my embryos remain frozen for?

The transfer of frozen embryos can be carried out until you are 50 years old. We will ask you regularly (every 2 years) if you still wish to keep your frozen embryos in order to try again in the future. There is no obligation, they remain in the clinic and they belong to you. The length of the time the embryos are frozen for does not affect their quality.

 

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