In intracytoplasmic sperm injection (ICSI), a single healthy sperm is injected directly into each mature egg. ICSI often is used when semen quality or number is a problem or if fertilization attempts during prior in vitro fertilization cycles failed. 

ICSI is a type of IVF. With traditional IVF, your healthcare provider places thousands of sperm next to an egg on a laboratory dish. Whether one of the sperm penetrates the egg to fertilize it is left up to chance. If none of the sperm fertilizes the egg, conception (also called fertilization) doesn’t occur. ICSI promotes fertilization through the direct injection of a single sperm into a single egg.