A blastocyst is an embryo at an advanced stage of physiologic development when there are two cell types present: one group of cells that form the placenta, and another group of cells that form the fetus. Advances by our superb IVF laboratory staff have been able to provide the proper nutrients to grow embryos in the lab to this advanced stage of development. The further developed the embryos, the better your ability to select the most viable embryos and ability to transfer a fewer number of embryos. This will allow us to maintain or raise pregnancy rates while reducing the number of embryos transferred, thereby reducing the most significant complication – multiple pregnancy.
A blastocyst is a highly differentiated, highly developed embryo that has grown to the point where it is ready to attach to the uterine wall (implantation). In naturally conceived pregnancies, the egg is released from the ovarian follicle and picked up the fallopian tube where it is fertilized by sperm. The resulting embryo starts out as a single cell, which then must grow and differentiate until it has the capacity to attach to the uterine wall. The embryo divides from one cell into two cells, then four cells, eight cells, 16 cells, etc. until it reaches several hundred cells at the time of implantation and reaches the blastocyst stage on day five or six after ovulation. The term “blastocyst” is a descriptive name to identify the developmental stage of the embryo.
The embryo spontaneously “hatches” from its shell (zona pellucida) at the blastocyst stage of development and is ready to attach to the uterine wall.