Sperm Preparation for Intrauterine Insemination (IUI)

by Dr. Susan Daniel

Although some semen may enter the uterus after intercourse, large amounts can cause painful uterine contractions. To avoid inducing contractions, sperm are separated from the liquid portion of the semen before they are used for intrauterine insemination (IUI). In the lab we call this procedure “sperm washing”.

There are two methods that we routinely use. The first method is separation by density gradient. Semen is layered on top of the gradient and centrifuged. Sperm are pulled through the gradient while the semen is left behind. The sperm that make it to the bottom of the gradient tend to be best quality sperm. Because some sperm get stuck and lost in the gradient layers, we prefer to use this method on normal semen specimens.

When the semen parameters are subnormal, we often choose to wash the sperm by resuspending the semen in culture medium and then separating the sperm from the semen by centrifugation. This method generally results in a better recovery of sperm, however, in addition to sperm, the preparation also contains dead sperm, sperm that are not moving, white blood cells, and debris.

Regardless of what method is used, the aim is to produce a preparation with enough motile sperm to optimize the chances of achieving a pregnancy.