Embryo
Cryopreservation is a procedure for freezing and storing embryos at a low temperature. Water in the embryos is replaced with a chemical solution (cryoprotectant) that prevents ice crystals from forming inside the embryos, as this would destroy them. Embryos are placed in liquid nitrogen and stored at -196°C. They may be stored this way for prolonged periods of time. When embryos are thawed, the cryoprotectant is removed and replaced with water. About 90% of good quality embryos will survive the freeze-thaw process.
Cryopreserved embryos are usually returned to the uterus during a menstrual cycle in which only supplemental estrogen and progesterone are taken. These hormones enhance the body’s natural cycle and ensure that the endometrium (lining of the uterus) is well developed. About 80-90% of the embryos will survive the freeze-thaw process, so we may need to thaw 3 or more depending on your age in order to obtain an adequate number of good quality embryos for transfer. You may be advised to delay use of your frozen-thawed embryos until after you have completed a 2nd IVF cycle in order to accumulate enough embryos before we begin thawing them. It is recommended that you wait at least two months following an IVF cycle before transferring frozen-thawed embryos. This allows your body a period of rest before attempting to achieve pregnancy again.