Embryo Freezing

Embryos can be frozen by a rapid freezing technique called “vitrification”. This type of freeze has resulted in significantly better embryo survival upon thawing and better pregnancy rates compared to the older “slow freeze” technique. We generally only freeze embryos that have developed to the blastocyst stage which occurs 5-6 days after egg retrieval. Embryos are stored in liquid nitrogen (minus 320 degrees Fahrenheit) until ready for transfer. A common question is “How long can my embryos be frozen?” The answer is that pregnancy rates upon thawing and transfer do not appear to be adversely affected by how long the embryos were frozen. The advantage of having frozen embryos is that with one retrieval a patient can potentially have several attempts to conceive with embryo transfer.

 There is an increasing body of scientific evidence indicating that pregnancy rates with transfer of a frozen/thawed embryo are better than pregnancy rates with a fresh transfer. The reason for this is not entirely clear, but it is thought that the uterus may be more hospitable for implantation in a frozen cycle than in a fresh cycle. Your doctor may recommend that you electively freeze all your embryos and delay transfer. If you had genetic testing on your embryos we will always freeze the embryos and delay the transfer while awaiting the genetics results.