Embryo Freezing

(Embryo Cryopreservation/ Blastocyst Vitrification)

Embryo freezing allows for the storage of unused embryos for an indefinite amount of time.  In vitro fertilisation and egg donation cycles often result in more embryos than are actually needed for transfer.  Remaining embryos which are suitable for freezing can be cryopreserved. A frozen embryo transfer can then be performed at a future time in a simple short procedure.

Today, embryo freezing has become a fundamental part of every clinic’s IVF programme, particularly when there is an emphasis is on singleton pregnancies. In many cases there are spare good quality embryos which can be frozen for later use – either to repeat the transfer cycle if the first does not succeed, or to be used for another baby if the first is successful.

Medfem Fertility Clinic has extensive experience in embryo freezing. With modern freezing techniques and greater experience, results from the transfer of frozen/thawed embryos are now almost as good as those with fresh embryos, so a store of frozen embryos can significantly add to the likelihood of pregnancy.

What is cryopreservation?

Cryopreservation is used in infertility programs mainly to freeze and store embryos from an assisted reproductive cycle (IVF, ICSI, PICSI).

What is vitrification?

Vitrification is an ultra-rapid method to freeze blastocysts instead of the traditional slow freezing process. By definition; vitrification is the process of converting fluid/matter into a glass-like solid that is free of any crystal formation. Vitrification of blastocysts yields better post-thaw survival rates and higher pregnancy and live birth rates from frozen embryo transfer cycles. Medfem Fertility Clinic began vitrification of blastocysts in late 2007 and have seen a considerable increase in post-thaw embryo survival rates as well as substantially higher pregnancy rates after frozen transfer procedures.

When do we vitrify?

From experience poor quality day 5 or 6 blastocysts/expanded blastocysts do not survive vitrification and warming. Therefore only good quality day 5 or 6 blastocysts/expanded blastocysts are vitrified and stored at -196ºC.

Storage in Liquid Nitrogen

Image Liquid Nitrogen Storage Tanks (2) Indications for Vitrification

  • Extremely good quality blastocysts/expanded blastocysts.
  • Blastocysts/expanded blastocysts of patients at risk of hyperstimulation syndrome are vitrified, warmed and transferred in a following cycle.
  • Poor uterine lining (endometrium), day 5 or 6 blastocysts/expanded blastocysts are vitrified and stored to be transferred in a more favourable cycle.

The blastocysts are warmed on the equivalent of Day 5 in either a natural or controlled cycle and transferred after an incubation period of 4 to 6 hours. Two hours after warming the viability of the blastocysts can be identified. Pregnancy testing is performed 10 to 12 days later.


  • Some blastocysts may not survive the freezing process. This is related to the quality of the blastocyst itself.
  • When reaching the vitrified stage and being stored at -196°C, the blastocysts are relatively safe from further damage. The DNA damage during cryogenic storage has suggested a maximum storage period of 1000 years.

Blastocyst implantation after FET

The embryo implantation process is not different from a fresh cycle. Pregnancy detection following blastocyst FET is possible with a sensitive blood assay for HCG hormone by 10 to12 days after a fresh or frozen blastocyst transfer.


  • The recovering rate after warming is 98%. Most of the patients scheduled for FET would receive 1 to 2 blastocysts on the day of transfer.
  • Pregnancy rate for a frozen embryo transfer (FET) is similar to a fresh cycle.
  • The average clinical pregnancy rate up to date for FET is between 46 and 52%.


The charge for vitrification (blastocyst freezing) is R9,245.00 (between 2-6 embryos). There is no storage fee involved for the first three months of storage. Thereafter an amount of R2,200.00 is payable per annum to secure the storage of semen, eggs and embryos.
(Prices valid until 31 January 2023)

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