Blastocyst Transfer

24 hours following your egg retrieval and fertilization, embryos should have divided to the 2-cell stage. After 48 hours, embryos should be 4 cells, and after 72 hours, normally developing embryos should be at the 8-cell stage. By awaiting an additional 48 hours (now the 5th day following egg retrieval), some of your embryos will, hopefully, develop into blastocysts (embryos >60 cells). Although we can assess and grade your embryos at 72 hours (8-cell stage), we cannot predict, with 100% accuracy, which of your embryos will continue to divide to the blastocyst stage.

As a general rule, only 30 – 40% of your 2-cell embryos will develop into good quality blastocysts. By allowing your embryos to grow in culture for 120 hours, our embryologists are able to grade and select your “strongest” and best embryos for transfer. If your embryos do not develop into blastocysts, this is a poor prognostic sign, and your chances of achieving a pregnancy are extremely low. Even though this outcome is difficult for patients to accept, thjs information is extremely valuable for us to determine where the problem lies i.e. either a potential egg problem, sperm problem or implantation problem. If your husband husband has normal sperm DNA fragmentation (sperm chromatin structure assay test), failure to produce any blastocysts may be indicative of an egg problem.

There are 4 theoretical advantages to performing a blastocyst transfer:

1) By selecting your stongest embryos on day 5, we believe these embryos give you the best chance of achieving a pregnancy.

2) We transfer only 1 or 2 blastocysts, thereby, eliminating high-order multiple pregnancies (triplets or greater)

3) A blastocyst transfer is more physiologic. If a pregnancy is conceived naturally, the developing embryo does not implant into the uterus until 5 days following fertilization in the fallopian tube. In a naturally conceived pregnancy, your embryo is at the blastocyst stage when it leaves the fallopian tube and enters the uterus. A blastocyst transfer, therefore, is more natural and physiologic compared to earlier embryo transfers. There are some studies indicating there are less uterine contractions on the 5th day following an egg retrieval (compared to more contractions on the 2nd and 3rd day). In theory, more uterine contractions could expel or prevent an embryo from implanting during a day 2 or 3 transfer.

4) Diagnostic reasons


Factors Affecting Implantation