Traditionally, IVF patients underwent transfer of their embryos at about day 3 after egg retrieval. This was considered acceptable and the norm. We are now seeing more clinics wait until about day 5 to do transfer to allow the embryos to reach what is called the Blastocyst stage.
With the improvement of the media culture in labs, the embryologists are able to sustain embryos longer, allowing them to further divide and reach the Blastocyst stage. During this stage they are considered to be much stronger and healthier than some of the embryos that were transferred at day 3. Waiting for a day 5 Blastocyst transfer allows the embryologists to have a better sense of which embryos have the greatest possibility of surviving transfer and implanting.
It makes sense that they are able to better predict the success rate. The reason for this is that when a pregnancy occurs without the use of IVF, implantation occurs in the Blastocyst phase. So, if you are transferring embryos that have already reached this stage, they are naturally better equipped for implantation.
Doing a Blastocyst transfer also decreases the risk of having a pregnancy with multiples as fewer embryos are transferred at one time. Since they are stronger and have a greater chance of surviving, there is no need to transfer more than 2-3 at once. This also typically leaves more to be frozen if you need to do IVF in the future.
However, typically the longer the embryos are kept in the media in the lab, the fewer there will be that survive. The reason being is that only the strongest of the embryos will make it to the Blastocyst stage in the lab. There is not any evidence that, even though the other embryos were not strong enough to make it in the lab, they wouldn’t make it through transfer either. It is possible that embryos not strong enough to make it to Blastocyst stage in the lab would make it if they were transferred at day 3. Many clinics will watch the embryos closely around day 3. If they feel like they are not going to make it to a day 5 transfer, they will go ahead and transfer them earlier to have the best chance of them surviving.
The experience of the embryologist can play a big role in transferring the embryos at the Blastocyst stage. Talk to your fertility clinic about their Blastocyst success rate, whether or not they tend to do a 3 or 5 day transfer and about the experience of their embryologist. Most clinics have a preference as to how long they wait to do a transfer and this can vary from clinic to clinic.
Research has shown that transferring embryos in the Blastocyst stage has a good success rate. However, since so many factors play into how long a clinic might wait to transfer, it is important for you to know that day 3 transfers still have a good success rate if they are good, strong embryos that are growing appropriately. Blastocyst transfer is fine for some people, but a day 3 transfer might be better for you if your doctor is unsure whether or not the embryos will make it any longer in the lab.127d
This entry was posted on Tuesday, June 13th, 2006 at 2:54 am and is filed under Fertility. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.