In the case of insemination, the male partner’s sperm is processed to achieve an optimal concentration for fertilization of the oocytes.
First, the semen is washed with a special solution and placed in a centrifuge in order to concentrate the sperm and separate them from the other components of semen. The pellet containing the sperm is then re-suspended in more of the same special solution while the remaining fluid is discarded. The oocytes are left in the cumulus-complexes, as this is required for the sperm to achieve their final activation steps.
A pre-determined concentration of sperm is placed in the drops of media that contain the eggs approximately four to six hours after the oocyte retrieval. The dishes containing the eggs and sperm are then returned to the incubator for 16 to 18 hours.