Embryo Cryopreservation (Vitrification)

What is Embryo Freezing? 

Embryo Freezing, or Cryopreservation, is a process of freezing IVF embryos for future transfers to achieve pregnancy. It is a compelling option run on specific Protocols designed for delaying transfers and/or preserving embryos for the Frozen Embryo Transfer (FET) cycles.  

Currently, the most effective technique for saving the IVF embryos performed by the IVF labs around the world is vitrification. It is added to most IVF cycles as a powerful back–up because it doesn’t affect embryos and has high survival rates, with an average of 96–99%.

Who is it for? 

• Single women undergoing an IVF cycle and having at least one top–quality IVF embryo suitable for Cryopreservation.
• Single men undergoing an IVF with Egg Donation stage of the Surrogacy process wishing to cryopreserve the remaining embryos. 
• Couples having the top–quality embryos after IVF or surrogacy and wishing to freeze them for future use.

When to try it? 

• In case of having elective single Embryo Transfer (eSET) in the current cycle.
• In case of wishing to have a back–up of extra embryos that can be used if an IVF with fresh transfer would fail. 
• In case of having top–quality IVF embryo(s) suitable for Cryopreservation and usage in FET cycle(s). 
• In case of Preimplantation Genetic Testing (PGT): vitrification enables the preservation of the embryos that have been biopsied until the Preimplantation Genetic Diagnosis PGD/PGT results are ready.
• In case of a canceled IVF cycle after egg retrieval or canceled Embryo Transfer (canceled on demand, if there is a high risk for developing an ovarian hyperstimulation syndrome (OHSS), the endometrium is not thick enough for making embryo implantation possible, if serum progesterone (P4) levels are greater than 20 ng/dl before the transfer — most likely, the embryo will not implant in the endometrium, and the IVF cycle would fail). 
• If you want to delay the transfer (for personal reasons, after undergoing DuoStimulation and two egg retrievals in one cycle, if you are taking the medication that may interfere with embryo implantation, or if you want to have the transfer in the next cycle)

How long does it take to cryopreserve an embryo?

Cryopreservation using slow–freezing technique takes up to 2 hours and involves two–staged cooling. In the first stage, the embryologists place embryos in a Slow Cooling Device and the embryos are cooled there very slowly — at a decrease of 3º–2º Celsius per minute until the cooling temperature reaches the final temperature — 196º Celsius (or about –321º Fahrenheit).

In contrast, vitrification is an ultra–rapid freezing technique that cools embryos so quickly to –196º Celsius that they become like glass or vitrified. Whilst the slow–freezing technique takes hours, vitrification is completed in minutes. 

Embryo Freezing Success Rates

With a classic slow–freezing Cryopreservation, survival rates for cleavage–stage and blastocyst–stage embryos range from 70% to 82%. With vitrification, survival rates for cleavage–stage and blastocyst–stage embryos range from 96% to 99%. 

In the vitrification versus slow freezing, the maximum survival rate is 99% vs. 82%, and the post–thawed (post–warmed) excellent morphology with all blastomeres intact (92% vs. 57%).