When an embryo grows up to day 5 or day 6, it is called Blastocyst. The Blastocyst has higher implantation rate (70%) as compared to day 2/day3 embryo (45%). So Blastocysts increase the chance of pregnancy, only that the patient must have produced a good number of embryos.
![Blastocyst / Embryo Transfer](https://anantivf.com/wp-content/uploads/2016/11/Blastocyst-Embryo-Transfer.jpg)