Frozen Embryo Transfer

Our cryopreservation program has been utilising the vitrification method since 2007. We have an astonishing pregnancy rate when using frozen vs. fresh embryos.

Frozen Embryo Transfer involves thawing cryopreserved embryos and transferring them to the female patient in a cycle that does not involve stimulation of the ovaries. The astonishing survival rate of vitrified embryos results in a high pregnancy outcome.

Vitrification is characterised as the second most ‘important invention’ in the IVF practice after Intracytoplasmic Sperm Injection (ICSI) due to its importance in the routine work of an IVF laboratory.  It is proven that in stimulated cycles endometrial receptivity is impaired due to stimulation drugs. Thus, a subsequent frozen embryo transfer could bypass this adverse effect and result in a successful pregnancy with similar or even higher pregnancy rate than fresh cycles. We are strong supporters of this idea, but more studies need to be conducted before we turn to a freezing all embryos strategy as a routine for all patients.

Vitrification of embryos at Pedieos IVF Center is used for:

  • Storing extra embryos from an IVF cycle

  • Patients with a risk of Ovarian Hyperstimulation Syndrome. Transfer will take place in a future non stimulated cycle with success rate similar to a fresh cycle

  • Poor responders due to age higher than 39 or low AMH. With these patients, we take good quality embryos from several natural or minimal stimulation cycles and vitrify the embryos. Normally, we will have a maximum of 1 or 2 good quality embryos created from each cycle. When a sufficient number of good quality embryos have been created and vitrified, the frozen embryo transfer can be scheduled, thus maximizing the chance of pregnancy for these patients.

  • Cases where embryos have to be biopsied for genetic testing (PGT-A, PGT-M, PGT-S). The embryos are cryopreserved following the biopsy so as to allow sufficient time for the genetic laboratory to return the results of the testing, which can take from a few days to a few weeks. When the results are in and there are ‘healthy’, transferable embryos, the female patient will be prepared for a frozen embryo transfer on her following menstrual cycle.

The process

The female patient takes medication to prepare the uterine endometrium to accept the embryo. This medication is not the same as in the stimulation cycle for the oocyte collection. Once the endometrium and the patient’s reproductive hormones are at an appropriate level, the embryos are thawed and transferred.

Frozen embryo transfer can be done either on cleavage stage embryos (Day 3) or blastocyst embryos (Day 5).

Please note that we perform Laser Assisted Hatching on all of our warmed embryos before transfer free of charge. Studies confirmed that vitrified embryos have a thickened zona pellucida, so assisted hatching helps to overcome this potential problem by allowing the embryo to hatch on the zona pellucida and be implanted onto the uterus endometrium.