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What’s in the Numbers: Explaining Post Thaw Motility and Total Motile Cells

August 29, 2011

Blog written by Laboratory Staff C.O.

At Fairfax Cryobank before we ship out any frozen unit to our clients, we are able to provide a series of calculations that let you and your doctor know the important facts you need as you decide on your best treatment.

We start by taking a small sample from each sperm donor ejaculate and set it aside from the units we ship to clients. This test sample is frozen separately and then thawed. It is examined under the microscope to look for the percent of sperm that are progressively motile (moving forward). Their forward movement is also graded on the scale of 1-4, four being the most forward motile. We require a minimum of a 2.5 grade for each specimen. When the post thaw motility (movement after thawing) is multiplied with the total number of sperm (count/mL) in the frozen semen specimen, you are able to calculate the number of Total Motile Cells (TMC). The TMC is the total number of motile sperm available to potentially reach the egg in order to fertilize it.

Although it takes just one sperm to fertilize an egg and achieve a pregnancy, it takes many more sperm than just one for pregnancy to reliably occur via insemination or intercourse. Research from many outside sources tells us that 10 million motile sperm is an ideal number to allow pregnancy to occur. More is not always better in this case. Many motile sperm do not reach the egg because the journey through uterus to the fallopian tubes is a long and difficult one. A small number of the motile sperm inseminated survive long enough to attempt to fertilize the egg. For those sperm that do complete the journey and reach the egg, penetration of the egg is far from assured because the egg is enclosed in a thick “shell” – the Zona Pellucida that only the sperm that are most motile, will be able to penetrate through and fertilize the egg.

We are confident that the quality of our donor sperm samples in conjunction with a plan from your physician will optimize your chance for pregnancy.

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