Blastocyst Culture & Transfer (BC)One of the most promising techniques for improving IVF success rates is the blastocyst transfer. A blastocyst is a many-celled embryo in the stage just prior to hatching, approximately five days after fertilization.
These blastocyst embryos have a much greater likelihood of implantng in the uterus. Improvements in our culture medium have given us the ability to allow embryos to metabolize more efficiently, and therefore we can maintain them outside of the human body for longer periods of time.
A blastrocyst transfer has many benefits. First, by observing embryos on day five we are better able to identify their quality and predict which will be the better candidates for successful implantation. Further, the embryos are arriving in the uterus at the same time as in natural conception, At day three an embryo is just entering the uterus from the fallopian tubes. The uterus is a more hospitable place to the five-day embryo as opposed to a two or three day embryo. Because we have the ability to improve implantation rates we can remove fewer embryos (2-3 instead of 4-6) and thus avoid the problem of higher-order (triplets or greater) multiple pregnancies.
Finally, preliminary evidence is showing that the longer you can keep embryos out of the uterus the more likely it is that they will not be expelled. Studies are showing that blood loss from the egg retrieval process causes uterine contractions in some women. If the uterus contract too many times in rapid succession the embryos will be expelled. By waitng five days to return the embryos to the uterus the body has a chance to reabsorb this blood and the contractions are greatly diminished.