Judging by the number of unwanted pregnancies that occur, you’d
think that all men are fertile. But for your pleasure to result in
pregnancy, all the systems in your nether region have to behave in
concert.
Your sperm must be present in sufficient numbers. It must be active, it must not be clumping together, it must conform to a shape and size, and it must not be negatively affected by the sperm antibodies present in you or your partner.
It must be able to penetrate the barrier of the woman's cervical mucus and overcome some fairly scary odds to even reach the fallopian tubes and go on to meet the egg.
If you and your partner find you’re unable to conceive despite applying yourselves repeatedly, your doctor may recommend a semen analysis to assess male factors which might be preventing fertilisation. Your sperm will be examined under the microscope.
You’ll be asked to provide a semen sample by masturbating into a clean, large-mouth, glass jar or plastic specimen cup, or by ejaculating into a special condom during intercourse. This is fairly simple stuff, but it’s important to keep the sample warm and to get the sample to the laboratory for analysis quickly. Many fertility experts want your semen within an hour.
The average, healthy man will have up to 600 million sperm in a single ejaculation. Semen contains sperm, water; simple sugars (it’s the sperm’s fuel); alkalies (to protect sperm against the acidity of the male urethra and the vagina); prostaglandins (substances that cause contractions of the uterus and fallopian tubes, and are thought to aid in the sperm's passage to the womb), vitamin C, zinc, cholesterol, and a few other things.
While semen can transport a variety of diseases, including the HIV virus, healthy semen contains nothing that's harmful to the health of your partner.