Excess embryos may remain after your in vitro fertilization (IVF) cycle and fresh embryo transfer. These embryos may be suitable for cryopreservation or freezing. Embryo cryopreservation provides the opportunity for additional attempts at pregnancy from a single IVF cycle.

During the freezing process, the embryos are placed in solutions that gradually remove the water from their cells. This protects them from damaging ice formation during freezing. They are stored at very low temperatures (-196ºC). When thawed, they are placed in a different series of solutions to add water back to the cells. These thawed embryos can then be transferred into the uterus for another attempt at pregnancy, without having to undergo the entire IVF cycle.

FAQs

Why should I freeze extra embryos after an IVF cycle?

Freezing extra embryos offers additional attempts at pregnancy from a single IVF cycle. Since these embryos have already been created, the risks, expense and inconvenience of ovarian stimulation and the egg retrieval procedure can be avoided. Also, it is often possible to perform a frozen-thawed embryo transfer in a natural cycle, that is, without any medications.

For how long can embryos be frozen?

It is currently not known how long embryos can be kept frozen before they are unable to cause a pregnancy. To date, successful pregnancies have been reported from transfer of embryos frozen for longer than ten years.