The semen analysis is only a rough assessment of sperm and does
not readily relate to sperm function. "Sperm concentration"
is an example of the inherent problems within the semen analysis.
* The normal range for sperm concentration is greater than 20
million sperm per milliliter, according to the WHO. This number
was derived by two urologists, MacLeod and Gold, in their research
that was published in 1951. The semen analyses of 1000 army men
from "fertile" relationships (defined as relationships
in which the wife had recently been pregnant) was compared to
the semen analyses of 1000 army men from "infertile"
relationships (loosely defined as the inability to achieve a pregnancy
from "a few months to 15 years"). The assumptions included
that the infertility problem was primarily due to a male factor
in the infertile relationships (since there is no accounting for
female factor infertility in these couples), and that each of
the men in the fertile relationships was necessarily responsible
for the pregnancies within those relationships. It was discovered
that only 5% of men in the fertile relationships and 16% of men
in the infertile relationships had sperm concentrations of less
than 20 million sperm per milliliter. Therefore, a sperm density
of 20 million per milliliter was established as the level under
which there is a greater chance of finding an infertility problem.
* Criticism of this work may include (a) that it was published
over 45 years ago, when sperm density ranges may have been different
than today (many recent reports have claimed to have found a decrease
in the sperm counts over the past few decades) and (b) the cutoff
of 20 million only "catches" 16% (about 1 in 6) of the
men in the infertile relationships (not a very sensitive test)
and includes 5% (1 in 20) of normal men (not very specific).
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