This procedure has revolutionized the treatment of male infertility since it allows couples to achieve fertilization, even when only a few sperm are available. The procedure was developed to overcome male infertility problems such as: low sperm counts, poor motility or movement of the sperm, poor sperm quality, or sperm that lack the ability to penetrate an egg. Later, the indication for ICSI has broadened and is performed to optimize fertilization in cases in which few eggs are available and for cases requiring PGD for single gene disorders. ICSI has revolutionized infertility management, to the extent that most treatments previously used have been abandoned in its favor.

ICSI is performed by physically inserting one sperm into each egg using a microscopic approach. Because only one sperm is needed per egg, even very small numbers of sperm will do. Once the egg is injected with a single sperm, it is observed approximately 18 hours later to see if fertilization has taken place.