OK, we know we cheated here by combing two terms in one. However, these two words both refer to one thing: sperm.
When a couple is trying to figure out why they can't conceive, doctors will examine the reproductive systems of both the man and the woman. One of the most important, and telling, tests a man can have is a semen analysis.
During this test, doctors evaluate the volume of semen produced (which should be from 2 to 6 milliliters) and how many sperm are in the semen (normal count is 20,000 sperm per milliliter) [source: University Hospital]. But they also examine sperm's motility, or how well they move, as well as their morphology, or shape. For sperm to be considered healthy, they must move steadily and powerfully forward, and not in a confused or circular pattern, as can sometimes be the case. This will allow them to find and penetrate the egg in the woman's uterus.
Sperm must also be well developed, having an oval-shaped head and a whip-like tail to propel them. Misshapen sperm sometimes have overly large heads, or double or bent tails. It's important to note that for a semen analysis to indicate a morphology problem, most of the sperm must be malformed -- having a small percentage of malformed sperm is considered normal.
If either the motility or morphology of the sperm falls below the normal ranges, problems with conception can occur. Doctors will frequently wait a month or so and perform another test. If problems still exist, further examination may be in order to determine if there's an issue with the man's reproductive system. Doctors will then look for issues such as testicular abnormalities or varicoceles, an enlargement of veins in the scrotum.