An essential part of any fertility health check is a sperm test or semen analysis. Here we will explain what is looked at in a basic sperm test and what information this gives us.
pH
The pH of the sample is the acidity and alkalinity, this is measured on a scale with 7 being neutral. Sperm functions best with a slightly alkaline pH, so the value should be equal to or greater than 7.2. The seminal vesicles and prostate both contribute towards the pH level. An acidic pH of below 7 may indicate blockage of the seminal vesicles. Occasionally infection or inflammation in the seminal vesicles or prostate can lead to a significantly raised pH.
Volume
Volume is another parameter that is measured. The volume in a sample should be above 1.4ml. Adequate volume in an ejaculate is needed to aid the transport of semen in the female reproductive tract. Low volume can be caused by a short abstinence period or incomplete collection. It is for this reason that abstinence is advised prior to producing a sample, for 2-5 days. Low volume can also be psychogenic, caused by difficulties with ejaculation. Medical causes are retrograde ejaculation (a problem with the ejaculate being directed internally), nerve problems or ejaculatory duct obstruction, or seminal vesicle disease. If the seminal vesicles, prostate or testes are small or have not been formed properly during development we may also see a low sperm volume.
Concentration
Concentration of sperm – the number of sperm per millilitre should be above 16 million/ ml. If the concentration is reduced below 15 million/ml, this is called oligozoospermia or low sperm count. Where there are no sperm seen in the sample, this is called azoospermia. There are a wide range of causes for low sperm concentration. These are:
- Infections
- Varicocele (dilated blood vessels in the testicle)
- Previous surgery to the testicle or hernia repair
- Being overweight
- Excessive alcohol, smoking or drugs
- Regular overheating of the testicles
- Hormone deficiency
- Use of anabolic steroids
- Undescended testicles as a baby
- Blocked, damaged or absent tubes (vas deferens)
- Chemotherapy
- Some medications
- Genetic problems such as Klinefelter’s syndrome
- Previous vasectomy
- Sometimes the cause cannot be identified
Total Count
The total sperm count in the sample (regardless of the volume) should be above 39 million.
Progressive Motility
This is the proportion of sperm that are motile and should be above 30%. Sperm need to be mobile, able to swim forwards in a progressive manner. Low sperm motility is called asthenosperma or asthenozoospermia. It is often seen together with a low percentage of normal sperm (see below).
Genetics, antisperm antibodies (see below) varicoceles and infections are some of the possible causes.
Normal Forms
The percentage of sperm that appear normal. The vast majority of sperm are abnormal in some way and will not fertilise an egg. There should be at least 4% that appear normal. Usually it is between 4-8%. The normality of the shape of the sperm affects its ability to bind to and penetrate the egg.
Exposure to chemicals, overheating of the testicals, infection and genetic factors can lead to abnormal morphology. This is also known as Teratospermia.
Sperm MAR % Bound
This is a measure of how many of the sperm have antibodies (infection fighting cells) bound to them. This happens if the body’s immune system attacks the sperm. This is significant if there is more than 40% MAR bound. This is commonly seen in men after vasectomy reversal, but can also occur after testicular injury or surgery.
Summary
Sperm tests are very useful to help identify the cause of infertility and guide treatment. If the results are abnormal, you would often be asked to repeat the test in 3 months time as it takes this long for sperm to be formed. This will help to rule out a transient problem such as intercurrent illness. If you have had an abnormal result you should consult a fertility specialist.