Cryopreservation of cleavage and blastocyst stage embryos has become a necessity, since frequently in an IVF cycle there is a greater number of high quality embryos than those transferred. These supernumerary embryos can be cryopreserved and stored for future use.

With the development of culture media and the use of vitrification, a rapid cryopreservation method that helps avoid the formation of crystals inside the embryo and thus osmotic shock and injury are avoided, survival rates of cryopreserved embryos are around 90%; pregnancy rates are also similar to those of fresh embryo transfers.

In addition, improved culture conditions can allow for the development of embryos to the blastocyst stage, which offers an embryo selection tool, thus maximizing pregnancy and implantation rates. This has resulted in the reduction of the number of embryos transferred per cycle and hence blastocyst cryopreservation has become an important and frequent procedure in the IVF field.

In what cases is embryo cryopreservation recommended?

Other than in cases of supernumerary embryos, freezing all embryos is also recommended in cases of suspected or confirmed Ovarian Hyper-stimulation Syndrome (OHSS) as OHSS severity is significantly reduced if fresh embryo transfer is avoided.

Additionally cryopreservation of all embryos is applied in cases where there are no optimal conditions for the implantation of embryos (for example in the presence of very thin endometrium) thus lowering the probability of a successful pregnancy.

Finally embryo cryopreservation can be used for fertility preservation. Women in a relationship who are not ready to start a family, or whose fertility will be compromised may opt to undergo ovarian stimulation, fertilization of the collected oocytes with their partner’s sperm and cryopreservation of embryos, whose developmental potential and quality have been verified.