Blastocyst transfer for IVF
Advances in the understanding of the growth requirements for embryos has fostered the development of new laboratory approaches in the culturing of embryos. One such advancement in IVF therapy is blastocyst transfer, also known as day five embryo transfer. The blastocyst stage is the point at which the embryo normally exists within the uterus and is usually capable of implantation.
With blastocyst transfer, fewer embryos are transferred to the uterus, which limits the possibility of high-order multiple pregnancies that often put the mother and babies at risk.
Though fewer embryos are transferred at the blastocyst stage, the pregnancy rates are similar to-if not higher than-when more embryos are transferred via the traditional IVF method. In addition, by waiting until day five, the embryos indicate by their rate of development which have the most potential to implant.
Blastocyst transfer for in vitro fertilization
Blastocyst or day five embryo transfer is an exciting new advance in IVF therapy. Since the birth of IVF technology in the 1970’s, IVF has involved the transfer of embryos at a relatively early stage of the egg retrieval. Embryos had generally reached the 2-4 cell stage of development at that time.
Beginning in the late 1980’s-early 1990’s, we started culturing the embryos a little longer, to the third day after egg retrieval, when we would expect the embryos to be about 8 cell stage development. The idea was that, by giving the embryos an extra day to grow in culture, we would be able to tell which embryos were growing "faster," and thus transfer embryos that may have a better chance of implanting and creating a pregnancy.
This approach worked pretty well, with pregnancy rates of 20-40% reported by many centers. However, several problems remained. First is the fact that embryos do not implant in the uterus at the 2-8 cell stage; growth must continue for several days in the uterus before implantation is possible. Normally, the 2-8 cell embryo is in the fallopian tube traveling towards the uterus. Thus, we were transferring embryos into an environment (the uterus) that wasn’t where they belonged under normal circumstances.
Second, we generally had to transfer multiple embryos (3-4 typically) into the uterus to help ensure that at least one would continue to develop an implant, leading to triplet pregnancies or greater. These multiple pregnancies carry much greater risks of complication for both the mother and the babies. On the other hand, it is possible that NONE of the embryos were capable of continued development. In this case, although we felt we transferred good quality embryos, pregnancy did not occur.
Transfer of blastocyst stage embryos on day 5 post-retrieval answers many of the above concerns. The blastocyst stage embryo consists of over 50 cells, and is the stage at which the embryo normally is capable of implantation. The embryo normally exists within the uterus at that stage. In the past several years, many advances have been made in our understanding of what embryos need to grow in the laboratory. In the past, only 20% or so of embryos could be grown to blastocyst stage, but with current techniques 40-50% of fertilized eggs can be grown to the blastocyst stage in culture.
Important advantages in blastocyst transfer
- Transferring embryos that have developed to blastocyst stage should help improve pregnancy rates, because we know the embryo has developed to a more advanced stage of development. In our program, our pregnancy rates have increased from about 40% per retrieval with the day 3 transfer to almost 60% per retrieval with day five transfer.
- Because the embryos have developed to blastocyst stage, we can transfer fewer embryos to achieve pregnancies, thus limiting the possibility of a triplet or greater pregnancy. Generally, with blastocyst transfer excellent pregnancy rates can be achieved by transferring only two embryos. Our most recent results suggest that 40% or more of transferred blastocysts are capable of implantation.
Assisted Fertility Services routinely provides day five transfer procedures for all of our IVF patients. We are happy to be able to provide this service, and we are committed to offering the most modern, state-of-the-art embryo transfer or any other aspects of assisted reproductive technology. For more information, call 317-621-2414.