Normally, millions of spermatozoa are deposited in the upper vagina. Out of these, only 10% are able to travel up to the cervix. Further, only 0.5% of these spermatozoa reach the fallopian tube and only a single spermatozoon is able to fertilize the oocyte. This is possible if and only with spermatozoa having normal physiology. Hence, when selecting the spermatozoa for IVF, those with normal physiology are selected for injecting the oocyte extracted from developed follicles.
PICSI has a higher success rate in developing good quality embryos resulting in good changes of implantation and pregnancy.