The procedure of Intracytoplasmic Sperm Injection (ICSI) involves direct injection of a single sperm into the an egg under the microscope, and its successful performance requires a high level of technical expertise in the IVF laboratory. When there is little or no sperm in the ejaculate (oligo or azoospermia), ICSI can be performed to accomplish fertilization with sperm obtained through microsurgical epididymal sperm aspiration (MESA), testicular sperm extraction (TESE) or testicular sperm aspiration (TESA). Some of the indications for ICSI include low sperm count or abnormal sperm parameters, congenital absence of the vas deferens, obstruction of the vas deferens (such as following vasectomy or trauma), testicular failure, erectile dysfunction, ejaculatory problems or a history of prior poor fertilization.

The introduction of ICSI has made it possible to fertilize eggs with sperm even in the most severe cases of male infertility. Approximately, 20-30% of conventional IVF is associated with unanticipated poor fertilization. This has led many experts to conclude that male infertility may be an occult phenomenon in some men. In fact, a new test called sperm DNA integrity assay (SDI or SCSA) have demonstrated that DNA damage may be present in sperm collected from men with normal and abnormal semen analyses.

A major advantage of doing ICSI is that, it allows the embryologist to remove the cumulus cells that enclose the egg and assess its maturity. This cannot be done with conventional IVF as the removal of these cells would virtually prevent conventional fertilization in the petri dish. Additionally, ICSI is utilized in cases of preimplantation genetic screening/diagnosis (PGT). In such cases, ICSI prevents DNA contamination from additional sperm, possibly increases the number of fertilized eggs (more embryos), thus allowing more embryos to be available for genetic testing and transfer.

It is important to know that when poor or genetically defective sperm (may still look normal) is used to fertilize the eggs utilizing ICSI, the genetic defects may be passed on to the embryo and thus the offspring. In such cases, the genetic defects related to the sperm may result in birth defects or other chromosomal abnormalities. It has been reported in the medical literature that babies born through IVF with ICSI (or those in need rather than the actual treatment) may be at an increased risk for birth defects compared to the general population. We now know clearly that the level of risk in the infertile population is higher than the general population. Therefore, it is believed that the increased risk of genetic problems and birth defects following IVF with or without ICSI are due to the risks associated with poor egg or sperm quality or genetic defects that may have caused infertility, rather than the procedures involved such as IVF and ICSI. This is further substantiated by the fact that even after IUI treatment the risk of birth defects is increased in the infertile population.