Embryo Freezing

Embryo freezing is commonly used to preserve embryos that have been produced, but that are not transferred to the uterus. To date, over 150,000 births have occurred from the transfer of previously frozen embryos, some having been frozen for more than a decade. Embryos are frozen using a computer-guided process resulting in a final temperature of -196⁰C. At this temperature the embryo ceases all metabolic activity until thawed. The thawing process, however, can lead to trauma and damage of the embryos, leading to a loss of viability. In general, the implantation rates of previously frozen embryos are approximately half that of fresh, never frozen embryos. Overall, pregnancy rates from frozen embryos are less than 30% per transfer.