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What’s in my vial of donor semen? (Part I)

January 20, 2011
Blog written by Fairfax Cryobank Director Stephen H. Pool, Ph.D.

I sometimes get questions related to semen and semen quality standards. Many sperm banks publish quality standards and although similar in some aspects, they are different in other areas. How do I understand what is in my vial of donor semen?

First, one needs to understand the terms used to describe a semen sample purchased from a sperm bank. Then, when reading the semen quality standard you should have a better understanding of what you have purchased. Here are some common terms used when referring to semen samples purchased from Fairfax Cryobank.

  • Semen - Semen is a mixture of fluids from the male accessory glands (prostate, seminal vesicles) sperm cells from the testes and other cellular debris (leukocytes, immature sperm cells, etc.). Frozen semen is packaged in straws or vials. Most straws contain 0.5 ml of semen and vials often contain 0.5 ml or 1 ml of semen.
  • Concentration – Concentration is the number of sperm per unit of volume. Sperm concentration is typically reported in millions per milliliter (ml). Example: 50 million/ml.
  • Cryoprotectant – The cryoprotectant is a substance (usually glycerol) that is added to the semen to help preserve/protect the sperm cells during the freezing process. The cryoprotectant is usually mixed in a media. The media can be an egg based buffer or a non-egg based buffer and is called the cryoprotectant solution or extender. By adding a cryoprotectant solution to the raw semen, the sperm cells are protected from dying during the freezing and thawing cycles. The cryoprotectant solution does not guarantee 100% survival however the number of sperm surviving the freeze-thaw cycle will be higher if a cryoprotectant is used than if it is not.
  • Percent (%) Motility – Percent Motility is the number of sperm cells that are moving in a semen sample divided by the total number of sperm cells (moving and nonmoving) in a specific volume (typically 1 ml).
  • Total motile cells (TMC) – TMC is a calculation of the Total number of Motile Cells moving in a specific volume (0.5 ml, 1 ml for example). You need three pieces of information to calculate the TMC. The concentration of sperm, the percent motility and the volume. The calculation is: Concentration (millions/ml) X % motility X volume (ml) = TMC. Example: 70 million X 35% X 0.5 ml = 12.25 TMC/0.5 ml.
  • Pre-freeze motility – % of sperm cells that are moving prior to freezing.
  • Post-thaw motility – % of sperm cells that are moving following thawing.
  • ICI ready or Unwashed semen – Unwashed semen is a semen sample that has not had the seminal plasma (liquid portion) of the raw semen sample removed prior to adding the cryoprotectant solution. Therefore, an unwashed sample contains all the fluids in the original sample plus the cryoprotectant solution. Unwashed semen is typically used for intracervical inseminations (ICI) but can be washed following thawing and used for intrauterine inseminations (IUI) or in vitro fertilization (IVF) or IVF/ICSI.
  • IUI ready or Washed semen – Washed semen is a sample that has had the seminal plasma (liquid portion) of the raw semen sample removed and replaced with a sperm compatible media plus the cryoprotectant solution prior to freezing. Washed semen is typically used for intrauterine inseminations (IUI) and does not need additional prep prior to insemination. IUI samples can also be used for ICI without further prep. IUI samples can be washed post-thaw and used for IVF or IVF/ICSI.
  • IVF unit – IVF units are unwashed samples that contain half the TMC of an ICI or unwashed semen sample. 

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