INTEGRIS Bennett Fertility



3433 NW 56th
Bldg. B, Suite 200
Oklahoma City, OK 73112

Blastocyst Transfer

Five days after fertilization, the embryo becomes a blastocyst. It has approximately 128 cells and a cavity full of fluid. Many embryo transfers in in-vitro fertilization (IVF) today are performed in the blastocyst stage. The human embryo typically will divide into six to eight cells three days after fertilization. Further division will normally result in a blastocyst five days after fertilization. The blastocyst is graded based on its appearance under the microscope. The best blastocysts are typically transferred to the patient’s uterus. Others may be cryopreserved (frozen) for future implantation if they are viable.

The advantage of transferring a blastocyst (day-five embryo) is that further culture in the laboratory selects the most viable and hardy embryos. Such embryos theoretically are more likely to survive and result in a pregnancy. Therefore, the number of embryos transferred may be reduced, resulting in a similar or better pregnancy rate than with day-three embryos, but with lower multiple pregnancy rate. At Bennett Fertility Institute (BFI), most embryo transfers are performed with blastocysts on day five.

The disadvantage of transferring blastocysts is in patients with low number of eggs and embryos, or if embryo quality is poor on day three. Waiting till day five may result in no embryos to transfer. At BFI, the decision to transfer on day five or day three is individualized to each patient. Even though we prefer to perform a day-five transfer, approximately 20 percent of our embryo transfers occur on day-three.