IVF refers to the formation of embryos from sperm and oocytes in the laboratory. Eggs are retrieved after the use of ovarian stimulation medications, and sperm is collected by either ejaculation or aspiration techniques. The sperm is either allowed to fertilize the eggs or is injected into an egg (ICSI). The embryos are cultured for several days and then placed into the uterine cavity. Extra embryos are frozen for future use (cryopreservation).