Why do we need blastocyst culture? On the day of egg retrieval, the egg and sperm are fertilized and cultured for 3 days to form a cellular stage embryo, which we refer to as a “blastocyst”, and if the culture is continued for 2 more days, i.e., 5 days after egg retrieval, the embryo will develop into a “blastocyst”. Generally speaking, a good quality embryo will eventually develop into a blastocyst. In other words, during the 2 more days of incubation, there is a process of elimination of the embryo itself. Therefore, we believe that for the same embryo, the blastocyst is more indicative of its growth potential, and that blastocysts have a higher rate of implantation and pregnancy than embryos. What are the risks of blastocyst culture? Blastocyst culture has been proven to be safe over many years of clinical practice and widespread use. However, due to the differences in embryo quality, there are unforeseen potential damages that may be caused to the embryos during blastocyst culture, such as: embryo arrest or even death, resulting in no embryos, blastocyst transfer or freezing in the current cycle. Blastocyst culture may also increase the incidence of monozygotic twinning. Patients who become pregnant with blastocyst culture may experience other pregnancy and delivery complications such as miscarriage, abnormal pregnancy, and fetal/neonatal malformations, just as with a natural pregnancy.