The third step:

If your sample is for analysis only then we stop at step 2. If its for treatment then this third step is required:
For treatment your sample undergoes a process called density gradient centrifugation. The lower and upper ‘gradients’ are carefully layered and the semen layered on the top. The sample is then centrifuged for 15 minutes. Clear ‘seminal plasma’ is retained on the uppermost part of the gradient after being centrifuged followed by a clear separation of white blood cells, debris and other cells. The immature, abnormal sperm are seen along the gradient based on their density and motility.
Highly motile normal sperm move actively to the bottom of the gradient and collect as a pellet. We then wash this pellet twice (again in a centrifuge) until finally we have the very best sperm which we then re-count and make a calculation of the total number of motile sperm (for Intrauterine Insemination ‘IUI’) or calculate the tiny volume of that sperm required to enable us to add 150,000 sperm to the eggs later for IVF.

Here’s a typical before and after schematic of a sperm sample on the left before preparation and one on the right after it. It is the sperm at the bottom of the right tube that we use for treatment having removed the abnormal sperm and dead sperm. Before treatment (after it has been centrifuged) we have to also wash the sperm and then effectively leave the sperm with ‘sperm food’ for an hour or two so that it is primed and ready to do when its time to meet an egg.

Image result for sperm preparation