Blastocyst Transfer

The principal cause for IVF to not be successful is the failure of the embryo(s) to implant in the uterus after transfer.  It is unclear why this should be, but various modifications of the IVF treatment have been tried to improve the chances of implantation. One of these is blastocyst culture.

Most embryos transfers are done on day 3 after egg collection. Some embryos do well in culture while others do not. It is hard to tell which type of embryos you have. If embryos are cultured in the laboratory for a longer period of time (day 5-6), they may develop further to the blastocyst stage. At this stage the embryo has differentiated and is made up of more than 100 cells and it is possible to identify groups of cells that will make up the placenta (trophectoderm cells) and the fetus (stem cells).

Growing embryos in the laboratory is a difficult process and the longer that they remain in culture the greater is the chance that some or all of the embryos produced by the IVF process will not survive. On the other hand, those that do survive, are believed to have a greater chance of implanting. Using new and advanced blastocyst culture methods the ability to grow embryos to the blastocyst stage has improved. Said differently, only the "best of the best" embryos make it to the blastocyst stage. Since blastocyst are "very good embryos" they tend to freeze and thaw very well. On the other hand, very good day 3 embryos, also freeze and thaw very well.

Approximately 40+% of the embryos from younger women and as few as 8%from older women may make it to the blastocyst stage. There is a risk; however, that none of the embryos would survive to the day of transfer if blastocyst culture is attempted. Therefore ACFS has strict criteria should blastocyst transfer be considered:

• The woman is 37 or younger
• There are 5-6 perfect or near-perfect embryos on the morning of day 3
• Normal FSH levels
• No failed attempts at IVF

Blastocyst transfer may also be attempted in a frozen embryo treatment cycle if the embryos were cryopreserved on day 3; however, it is recommended that the above criteria are met.

At ACFS, the embryologist or physician will discuss with you the condition of your embryos and based on their development and quality, will recommend either converting to a day 3 transfer or continuing on to blastocyst transfer.

ACFS recommends growing embryos to the blastocyst stage (day 5) if the above criteria are met. In our experience, ACFS gets slightly highly pregnancy rates with a day 5 blastocyst transfer.  Even if a woman is not able to do blastocyst transfer, ACFS has excellent rates with a day 3 transfer.

A couple should understand that blastocyst transfer is relatively new and that animal studies have raised concerns about neonatal problems such as increased birth weight and fetal abnormalities. There is no evidence at the present time of similar problems following the transfer of human blastocysts.