Sperm washing is performed on semen samples that will be used for Intrauterine Insemination (IUI), In Vitro Fertilization (IVF) or IVF with Intracytoplasmic Sperm Injection (ICSI). The sperm washing process facilitates the segregation of motile sperm from immotile sperm, dead sperm and seminal fluid.
Procedures requiring sperm washing
Sperm washing is important for patients planning to have an IUI. During natural conception, the vagina and cervix act as automatic ‘sperm washers,’ removing seminal fluids containing prostaglandins, which can cause cramping in the uterus. After sperm washing, the isolated motile sperm are placed directly into the uterus, bypassing the vagina and cervix, bringing the sperm into close proximity to the fallopian tubes, where eggs are fertilized.
Sperm washing is used to prepare semen samples for IVF and IVF with ICSI as well. The separation of motile sperm allows the embryologist to add the motile sperm into a petri dish, containing eggs for IVF. To fertilize eggs for patients using IVF with ICSI, each sperm is individually selected using a micro tool on a powerful microscope, and then directly injected into an egg. Removing unnecessary debris from a semen sample allows the embryologist to pick sperm easily, without clogging the micro tool.
The sperm washing process
After a semen sample is collected, the andrologist allows it to liquefy for approximately 20 minutes on a warmer. The sample is then assessed for sperm count, motility, progression, volume and viscosity. Once all the parameters are determined, the semen is placed in a test tube, on top of two liquids with different densities (called a “gradient”), which will act as a filtering system.
The gradients contain silane-coated silica particles in a specific concentration. The top gradient is less concentrated than the lower gradient. The semen and gradients are then centrifuged, causing the seminal fluid to be trapped in the top layer, non-motile sperm in the middle layer, and motile sperm in a pellet at the bottom. The pellet of motile sperm is re-suspended in another liquid media, and the concentration, motility and progression of the sperm are evaluated. The sample is then ready for IUI, IVF or IVF with ICSI.