Embryo freezing (EF) is where embryos obtained from in-vitro fertilisation (IVF) are frozen and kept for later use. This is different from egg freezing, where eggs harvested from ovaries are directly frozen (without fertilisation from sperm) and kept for later use.
EF is most commonly done when surplus embryos are produced from an IVF cycles and only 1-2 embryos are being transferred back into the uterus. EF allows a woman to have a future chance of pregnancy if her initial embryo transfer is unsuccessful – without having to go through the whole IVF cycle again. You can read more about the process of IVF here.
Another common reason is “freeze-all”. This is where a woman needs time to recover from her egg collection e.g. high risk of developing ovarian hyperstimulation syndrome (OHSS). Freezing all embryos and allowing her time to recover means a frozen embryo transfer will be planned at a later date.
Another reason why EF is done is when a women in her reproductive age desiring children is diagnosed with cancer and need to undergo treatment e.g. chemo- or radiotherapy which potentially affects her future fertility. EF in this case can preserve her fertility and allow her to have her own children with her partner after recovering from cancer.
The most common method of EF is vitrification, where cryoprotectants are used to prevent formation of ice crystals during rapid cooling.
Studies have shown that the freezing and thawing process, and the duration of storage does not affect the babies which result from these frozen embryos. Pregnancy rates from frozen embryo transfers may in fact be better in certain cases.
About 85% of embryos survive the thawing process.
Read more about social egg freezing in Singapore here.
