What is a blastocyst? A blastocyst pregnancy is similar to a viable pregnancy because the blastocyst embryo is transferred into the uterus at nearly the same time that a natural pregnancy embryo enters the uterus. Within 5 or 6 days of fertilization 60 to 100 cells are distributed in two layers. During the blastocyst stage, the embryo enters the uterus and attaches itself to the uterine lining or endometrium, a process known as implantation, which is a critical step in development of the fetus. An intriguing question is , “Can you call a blastocyst a baby?”
