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Updated 25 July 2012

Semen analysis

Semen analysis is a laboratory test in which semen is examined under a microscope.

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What is a semen analysis?

Semen analysis is a laboratory test in which semen is examined under a microscope. Semen (the Latin word for seed) consists of sperm cells and fluid (seminal plasma). Sperm cells are produced in the testes (the male reproductive glands). Seminal plasma is produced mainly in the seminal vesicles (two little sacs situated under the urinary bladder) and the prostate (a gland situated at the bladder neck). Semen analysis is also known as a “sperm count”.

Sperm cells are transported from each testis through a thin tube called the vas deferens to the seminal vesicle where the semen is stored. From there a thin tube (the ejaculatory duct) passes through the prostate and opens into the urethra, the tube which carries urine from the bladder to the outside.

At the high point (orgasm) during sexual stimulation about 2-5 ml of semen is squirted (ejaculated) from the seminal vesicles to the tip of the penis. Sperm cells form less than 2% of the ejaculate, the rest is fluid (seminal plasma). A sperm cell consists of a head and a long tail, which moves with a whip-like action to propel the sperm cell forwards, so it looks like a tadpole swimming through water. The head of a sperm cell is about 5 micron, and the tail about 45 micron long (a micron is one thousandth of a millimetre).  

Why is semen analysis performed?

  • The most common reason is infertility, which is inability of the couple to produce a pregnancy after a year of regular intercourse without using anything to prevent pregnancy (contraception).
  • After vasectomy it is essential to do a semen analysis. Vasectomy is a surgical procedure where a small piece of the vas deferens is cut out and tied off so that the man becomes sterile, i.e. is not able to father children. For 2-3 months after vasectomy the semen still contains sperm cells which were stored in the seminal vesicles, so the couple should continue using other forms of contraception. Semen analysis is essential 2-3 months after vasectomy to confirm that there are no more sperm cells in the semen, and only then can the couple stop using other forms of contraception. 
  • Semen samples may be collected to help an infertile couple by means of in vitro fertilization (IVF). In vitro is Latin for “in glass” and it refers to the test tubes used in a laboratory, so this is where the term “test tube baby” comes from. Sperm cells are taken from the semen, egg cells (ova) are obtained from the woman’s ovaries, and the sperms and ova are placed together in a test tube so that the egg is fertilized, after which it is placed back in the woman’s uterus (womb) to develop into a baby.
  • Semen samples can be obtained to store them for future use, e.g. when the man has cancer of the testis and is going to be treated with drugs that will damage sperm production. Freezing and storing sperm samples is known as cryopreservation.
  • In rare cases where there is blood in the ejaculate (hemospermia) the semen may be sent for bacterial culture to see if there are germs in the semen.

How is semen analysis performed?

The semen parameters that are evaluated in the laboratory include the:

  • volume of the ejaculate – normally 2-5 ml
  • number of sperm cells (sperm count) – fertile men have 70 to 100 million sperm cells per ml of ejaculate
  • appearance (morphology) – more than 15% of the sperms should look normal
  • movements (motility) of the sperm cells – normally more than 50% should move in a forward direction.

The following are some of the terms used to describe sperm abnormalities:

  • azoospermia – no sperm cells in the semen
  • oligospermia – a low number of sperm cells (less than 20 million per ml)
  • teratospermia – a high percentage of abnormal looking cells
  • asthenospermia – a high percentage of cells that do not move (i.e. that are immotile).

How should I prepare?

You will be asked to refrain from ejaculating for at least 3 days before providing a fresh semen sample to the laboratory. The sample is usually obtained by masturbation, where the penis is stimulated manually (with a hand) to reach an orgasm. The ejaculate is collected in a wide-mouthed, dry, sterile container provided by the laboratory. It has to be kept at body temperature and must be examined within 1-2 hours after ejaculation.

If you are not willing to provide a sample by masturbation, an alternative is to have intercourse using a special condom for semen collection provided by the laboratory. Ordinary condoms should not be used, because they often contain substances which kill or damage sperm cells. Another option is to obtain the sample by interrupting normal intercourse at the moment of ejaculation, but this is not ideal, because some of the ejaculate may be lost, and germs or acidic secretions from the vagina may damage the sperm cells.

What are the risks? 

There are no risks or side-effects involved in providing a semen sample.

What are the limitations of the procedure?

    • There are different methods of counting sperm cells or evaluating the sperm morphology under the microscope, so different laboratories may give different reports of the same sample. Therefore, it is important to do all repeat semen analyses using the same laboratory.
    • Semen analysis is not able to separate patients definitively into fertile and sterile groups. As the semen parameters decrease, the chance that the man will father a child becomes less, but it does not reach zero. Only if there are no sperm cells in the semen (azoospermia) can it be said that the person is definitely sterile.
    • There are factors that have temporary adverse effects on the semen, so that the semen analysis is abnormal, but if these factors are removed, the semen may return to normal. Therefore, it is necessary to examine at least 2 semen samples at least 3 months apart before final conclusions can be made.
     
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