The suitable embryos that are not transferred in an in vitro fertilisation cycle can be frozen and used in future attempts at pregnancy
During an in vitro fertilisation cycle several embryos are generated for transfer to the woman’s uterus. Although the law provides for the possibility of transferring up to 3 embryos, in some cases we only transfer one or two. What will happen to the remaining embryos that are ready to be transferred? Today, cryopreservation is an established technique with good success rates, which makes it possible to take full advantage of the remaining embryos from an in vitro fertilization cycle for future attempts.
“Every embryo is unique, and that is why we give every opportunity for it to develop and be suitable for freezing, so that we can use it in the future,” explains Dr. Aïda Pujol, a biologist at the Eugin Clinic laboratory. “Once the embryo, or embryos to be transferred, is selected,” she adds, “the rest are left in culture in the laboratory for up to a maximum of six days from the time of insemination, which is the maximum period for their transfer, in order to freeze those that may be suitable for a new transfer, which we call cryotransfer”.
A safe technique
Cryopreservation of embryos is a very safe assisted reproduction technique, which today brings good results. In fact, nine out of ten embryos that are frozen are in perfect condition after thawing.
“The pregnancy rates in IVF cycles with frozen embryos are very good,” says Dr. Pujol. “For this reason, provided that an embryo meets the established criteria, we freeze it,” she says.
In vitro fertilisation using cryo-preserved embryo transfer is a convenient process for patients, since it allows them to organize their trip to the clinic more easily. In addition, with this technique, the patients follow a simpler medication regimen and can schedule what day they prefer to undergo the embryo transfer.
Embryo freezing is done by the vitrification process, which takes less than ten minutes. After applying liquid nitrogen to them, the embryos are preserved by vitrification in nitrogen vapor tanks, where they will remain available and in perfect condition -controlled and monitored in detail – until they are thawed and transferred to the future mother.