An embryo which has developed to the point of having 2 different cell components and a fluid cavity is reffered to as Blastocyst. Human embryos from in vitro fertilization in culture in an IVF lab, or developing naturally in the body, usually reach blastocyst stage by day 5 after fertilization. Blastocyst transfer with IVF can give high pregnancy success rates with very low risk of triplets. There are 3 distinct parts to a blastocyst - the two cell types and the fluid cavity. As development of blastocysts progresses, cells in the 2 components divide and the fluid cavity enlarges. With continued blastocyst development the embryo expands, the shell thins, and it hatches from its shell and implantation into uterus is then easier.
Our IVF centre practices Blastocyst transfer as there are two advantages: