Procedure for Sperm ‘Washing’
The seminal fluid facilitates not only the ejection of the sperm, but also their mobility. The semen acts as a mode of transport for spermatozoa, and may even provide the first layer of protection against thick cervical mucus. Large semen volume, however, can dilute the sperm and therefore reduce the number of spermatozoa reaching their intended destination. To ensure that only the most vigorous of sperm are introduced into the uterine environment, a procedure known as ‘washing’ occurs.
- The swim-up method collects the most motile sperm by introducing a special culture medium placed above the semen in a test tube. The sperm that ‘swim-up’ to the culture medium are harvested and injected into the womb.
- The density gradient column collects the most viable specimen by separating the motile (very dense) from immotile sperm, pus cells and seminal plasma (less dense). Because recovery rate is high and rate of infection low, this method of sperm washing is the standard technique in use today.