Embryo freezing (Cryoprservation)

What is Cryopreservation in IVF(In vitro fertilisation) ? 

Cryopreservation in simple language means freezing of the embryos. Eggs are fertilized in the IVF(invitro fertilisation)lab with sperm; embryos develop which are then transferred into the uterus. Successful implantation of the embryo following this fertilization process in the IVF lab(invitro fertilisation lab) is an extremely important variable affecting IVF success rates. Optimal success rates usually require an average transfer of two or three embryos. However, it is not unusual for 8, 10 or occasionally more eggs to be retrieved and therefore more than 3 embryos may be produced in an IVF cycle if desired. With the technique of embryo cryopreservation (embryo freezing) embryos developed but not transferred can be cryopreserved and stored for future use.

What is the advantage of storing these embryos?

There are many advantages of Cryopreservation in IVF(In vitro fertilisation):
  1. Patients who did not achieve successful pregnancies in that particular cycle in IVF(In vitro fertilisation) may use these stored cryopreserved embryos in the next cycle. Such a cycle is called "frozen embryo transfer” cycle. Here, one or more of the embryos are thawed and transferred to the lady’s uterus in a much less complicated cycle. Patients choosing this option can minimize their time, expense and the need for repeat egg retrievals.
  2. Patients having successful pregnancies from their "fresh" IVF (In vitro fertilisation) can use their frozen embryos for a second child after a few years.
  3. Embryo cryopreservation in IVF(In vitro fertilisation) also allows patients and physicians the possible option of reducing multiple births by controlling the number of embryos transferred and, at the same time, maximizes the efficiency of the fresh cycle they have already gone through.
  4. In patients with a risk of severe ovarian hyperstimulation (a rare but serious complication of IVF(invitro fertilisation) when a transfer of "fresh" embryos in that cycle would put the patient at high risk, all of the embryos are frozen and later warmed and transferred to the patient at a later time.

What is Vitrification in IVF(In vitro fertilisation)?


Vitrification is a newer technique to freeze embryos. Here, the embryo formed in the IVF(In vitro fertilisation) cycle is coated with a cryoprotectant and rapidly dipped in liquid nitrogen in a much shorter procedure. With the older slow-freeze technique, water, normally found in and between embryo cells, is frozen into ice crystals. As these embryos are thawed for transfer, the crystals can cause damage, which may lead to cell death. With vitrification, water is sealed out and embryos are "warmed," potentially resulting in less damage and hopefully higher pregnancy rates.