What happens to the frozen embryos from an in vitro fertilisation cycle?


In an in vitro fertilisation (IVF) cycle, viable embryos that are not transferred to the mother’s uterus are frozen and cryopreserved in liquid nitrogen in order to ensure that their reproductive potential remains intact. These embryos can be thawed and transferred in subsequent cycles whether this be because:

  • The patient has not become pregnant in the first IVF cycle and they want to try again.
  • The couple want to enlarge the family after a previous successful attempt.

But since medicine is not an exact science, it is common that once their reproductive aims are satisfied (and they do not want to have any more children) some frozen embryos are left over.

Although the assisted reproduction centres take care of their correct preservation and storage, it is the biological parents, i.e., either the mother (in the event she does not have a male partner) or the couple, who are responsible for deciding what should happen to their frozen embryos.


Possible uses for any remaining frozen embryos

  • Donation for reproductive purposes: in other words, donating the embryos so that they can be transferred into another woman’s uterus.

- The donation will always be anonymous, for both the parents and the woman receiving it.

- In order to choose this option, the eggs and sperm (which have fertilised the embryos) must meet the legal requirements for reproductive cell donation (the woman’s age at the time of treatment <35 years, negative serologies, family history, etc.)

  • Donation of the embryos to research projects. This is always in authorised centres under the strict control of the health authorities and after a favourable report from the National Commission for Assisted Human Reproduction (CNRHA in its Spanish initials). 
  • Letting them thaw without using them for any reproductive or research purposes. This option is only applicable when the patient is over 50 years of age (medically, it is considered no longer advisable to become pregnant) or because there are medical grounds that make a new pregnancy inadvisable because of the risk it might pose to the mother or the future baby.


Every two years, the woman or the biological parents are asked to renew and amend the previously signed consent on the how their frozen embryos will be used. Thus, they can state whether they have changed their mind or they wish to keep to their chosen previously option.



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