Sperm preparation

Husbands are asked to collect semen samples immediately before oocyte recovery. It is very important, as a general rule, that the egg recovery cannot proceed until the semen sample has been obtained and prepared. The sperm sample is assessed in the laboratory and a suitable method of preparation is used to isolate the most active sperm for insemination of the eggs.  ( If it is possible that the husbands may not be present for the procedure or if there is difficulty in producing samples , special arrangements can be made with couples for the freezing of semen samples prior to the day of egg collection. )

Three simple sperm preparation techniques are described in the following sections. Sterile techniques and materials are essential when applying a sperm preparation technique for therapeutic applications.

1. Simple washing

This simple washing procedure provides the highest yield of spermatozoa and is adequate if semen samples are of good quality.

2. Gradient separation

Discontinuous density gradients can provide the best selection of good-quality spermatozoa, giving good separation from other cell types and debris. This method uses centrifugation of seminal plasma over density gradients consisting of colloidal silica coated with silane, which separates cells by their density.

In addition, motile spermatozoa swim actively through the gradient material to form a soft pellet at the bottom of the tube. Sperm preparation using density gradient centrifugation usually results in a fraction of highly motile spermatozoa, free from debris, contaminating leukocytes, non-germ cells and degenerating germ cells.

3. Swim-up

Spermatozoa may be selected by their ability to swim out of seminal plasma and into culture medium. This is known as the “swim-up” technique. The direct swim-up technique can be performed either by layering culture medium over the liquefied semen or by layering liquefied semen under the culture medium. Motile spermatozoa then swim into the culture medium.