ICSI is accepted as a standard treatment option for infertile couples with severe male factor infertility. In most clinics, approximately 50% to 90% of the eggs that are injected with sperm using ICSI will fertilize normally.

Some eggs do not survive after injection with the sperm and subsequently degenerate.

The criteria regarding what constitutes severe male factor infertility, however, vary from clinic to clinic. Some clinics use ICSI for all (or nearly all) patients based on the theory that assisted fertilization is better than no fertilization at all, but most clinics employ ICSI based upon specific sperm parameters. In general, ICSI is employed in cases where the semen analysis reveals abnormalities related to sperm count (less than 20 million/mL), sperm motility (less than 50% are motile), or sperm morphology (less than 30% have a normal shape). ICSI should also be considered in couples with no previous evidence of fertilization or a history of failed fertilization with a prior IVF attempt. ICSI must be used in cases of sperm obtained from the testicle or epididymis in men with azoospermia (see Question 31). Some clinics use ICSI in all cases of IVF with frozen donor sperm.

Not all cases are clear-cut, for example, in our clinic we often perform an IVF/ICSI split if sperm parameters are normal but the couple has no previous pregnancies. That is, the eggs that are collected during the oocyte retrieval phase are divided between normal fertilization and ICSI. If some component of male factor infertility is present, splitting the eggs between ICSI and IVF may reveal whether the sperm can actually fertilize an egg. If the eggs fail to fertilize with IVF but fertilize normally with ICSI, then the logical conclusion would be that the sperm is incapable of fertilizing the egg with IVF alone. Couples with unexplained fertilization failure with IVF may have a problem with the sperm, the egg, or both. In such cases a repeat cycle of IVF using ICSI will usually yield good fertilization results and, ideally, a pregnancy.