Frozen Embryo Transfer (FET) Can Be the Answer to Your Problems with the IVF Process
Frozen Embryo Transfer (FET) is when embryos are frozen after they are created and implanted at a later date. Until the flash freezing process known as vitrification was introduced a decade ago, frozen embryos had a very low implantation and live birth rate. There were various reasons for the low numbers.
One of the primary issues was the freezing process itself, with the slow freezing method ice crystals formed within the embryo which damaged it to the point it often wasn’t viable anymore. Because the success rates for thawed embryos was so poor, the only embryos that were frozen were the embryos that were not deemed healthy enough to use during the transfer that was the most likely to succeed, the live embryo transfer.
With the improvements in the freezing process, and improvements in the process of selecting embryos, frozen embryos are being used frequently with results equal to those of fresh embryo transfers. Here are a few things to keep in mind when you are deciding whether to go with a frozen embryo transfer or traditional fresh embryo transfer.
- The flash freezing process, called vitrification, that is used now to freeze the embryos is 60,000 times faster than the old freezing method and doesn’t damage the embryos. With this system, over 90% of the frozen embryos survive thawing and are the same quality as fresh embryos.
- Embryos are now being saved at the blastocyst stage, 5-6 days after fertilization, instead of the cleaved state, 2-3 days after fertilization. The larger embryos are more likely to be chromosomally normal and viable, this embryo size is preferred for both FET IVF and fresh IVF because when you use healthy embryos you don’t need to implant as many. The cleaved state embryos haven’t had as much chance to develop so they are more likely to be chromosomally compromised, or aneuploid, and not develop.