Two to five days after egg retrieval, embryo transfer in which embryos are placed into the uterus of the woman, takes place. This is a simple and painless process that takes a few minutes and resembles to the Pap test process. No anesthesia is required for embryo transfer and it is performed under abdominal ultrasound monitoring.
On the day of embryo transfer, biologists select the best embryos, which are placed on the uterine bottom with a special fine catheter. After embryo transfer and for the next 9-12 days, the woman should avoid intense activity. It is mandatory to perform blood pregnancy test (β-chorionic gonadotropin) on the 14th day after ovulation. At the end of the process Dr. Ioannidis will hand out a written report to the couple on the entire course of the IVF cycle and photographs of the embryos implanted.
When embryo transfer occurs two days after egg retrieval, the embryos are at the 2-4 cell stage, on the third day at the 4-8 cell stage, and if the transfer is on the fifth day the embryos are in the blastocyst stage [link].
According to the Greek law [link] up to 3 embryos only can be transferred when the woman’s age is under 40 years or up to 4 embryos when the woman is over 40 years. Dr. Ioannidis will advise you on the number of embryos he recommends you to have implanted, but the final decision is yours. This decision will depend on the quality of the embryos, the age of the woman and the number of assisted reproduction attempts she has had in the past.
In a nutshell, embryo transfer has to:
- be technically flawless,
- take place using special-purpose catheters of the latest generation that are more visible during the ultrasound and do not injure the cervix,
- be performed at a time that will not leave the embryos long outside the incubator,
- take place imperatively under the guidance of the abdominal ultrasound scan.
Blastocyst is the stage of the embryo on the 5th day of its development, it consists of about 120-150 cells and is already beginning to differentiate into trophoblast (peripheral cell layer that will later form the placenta) and into embryoblast (inner cell mass from which subsequently forms the embryo).
Blastocyst culture is a technique that allows the selection of those embryos with proven potential for further development. This method has an indication in couples with a good number of embryos, usually over 6.
In recent years, efforts have been made to reduce multiple gestations by reducing the number of embryos transferred. One way to do this, without reducing the chance of success, is to transport blastocysts.
In theory, the advantage of transferring blastocysts is that this way better quality embryos are selected, according to the natural selection process, which increases the chances of achieving pregnancy. In addition, the transfer of blastocysts resembles to the natural process where the embryo reaches the uterus through the fallopian tube and is implanted between day 5 and day 6.
The great disadvantage of blastocyst culture is that not all embryos reach the blastocyst stage. This sometimes results in the risk of “losing” embryos that were perfectly healthy.
The new innovative technique of monitoring embryo divisions from fertilization using the time-lapse technique seems to replace the need for having the embryos develop into a blastocyst.
In the Assisted Reproduction Unit of MITERA Maternity Hospital, we were the first to apply the time-lapse method and it has been shown from the beginning that it is superior to blastocyst cultivation, which is fully consistent with the world’s bibliographic data. This allows us to select the best embryos already from 2nd or 3rd day and implant them, without taking any risks for the embryos. Of course in laboratories of IVF units that do not have these state-of-the- art infrastructures, it may be better to still use the conventional blastocyst technique.