Blastocyst formation is a good indicator for attainment of assisted reproduction.

Blastocyst formation is a late stage of embryogenesis before implantation. The examination for the percentage of blastocyst formation (PBF) can predict the viability/pregnancy of the assisted reproduction trials. The PBF significantly correlates with age and pregnancy. The PBF is significantly lower in the intracytoplasmic sperm injection (ICSI) treatment than the conventional IVF treatment. The zygotes from immature oocytes give less blastocyst formation than the zygotes from mature oocytes. One pronucleus "zygotes" have significantly less chance to blastocyst than the normal 2 pronuclei zygotes. A mathematical model is proposed, verified, and predicts the hatching/hatched is the rate limiting step for the outcome of pregnancy.