ICSI and embryo development

The process of fertilization in intracytoplasmic sperm injection (ICSI) treatment is largely different from that of physiological fertilization. It is also true that the rate of development of the embryo into the blastocyst after ICSI is lower than that after in vitro fertilization (IVF) [1,2]. It is unknown whether these facts are closely related. Although it is impossible to simply compare the results of IVF and ICSI due to the difference in their indications, it has been determined that pregnancy rates, the endpoint of fertilization failure treatment, are similar between ICSI and IVF treatments. This is because negative impacts of ICSI on fertilization do not become apparent due to a considerable effect of the in vitro culture environment. In this report, we discuss causes for the low development rate of the blastocyst after ICSI.