The Patient's Guide to Embryology

Semen analysis results explained

Semen analysis results determine what treatment options are available to you and can make a significant difference to your chance of success.

A semen analysis is essential if you are investigating your fertility and the results make a big impact on your IVF treatment. They determine what treatment options are available to you and can make a significant difference to your chance of success. Many factors can affect the results – some are out of your control such a hormone levels, but many lifestyle factors affect your sperm more than you think. Diet, smoking, drinking, age, drugs, recent illnesses, hobbies and the environment around you can all impact sperm production and sperm health. It is also very common for semen analysis results to fluctuate naturally over days and months.

It takes around 3 months to make a sperm cell from start to finish so remember that the results of a semen analysis today are a reflection of your health and lifestyle 3 months ago.

Semen appearance

This is the first thing an embryologist will check and it can be a good indicator of the sample quality, it is also something you can check yourself at home.

A normal semen sample should be at least 1.5ml and it should look white/grey.

Semen is clumpy and gelatinous when it is first ejaculated but it should turn into a liquid within 30 minutes.

Typically a more opaque sample suggests more sperm are concentrated in it, whereas a very watery, clear sample can suggest the sperm numbers are low.

Semen which is tinted with red, green, brown, yellow or black is abnormal and suggests there is an underlying health problem. A volume which is too high or too low indicates a problem with the fluid glands that mix with the sperm cells to make up semen.

Sperm concentration

The number of sperm in a sample is one of the most important measures of testicular function. Sperm concentration is reported as the number (in millions) of sperm cells in each millilitre of semen fluid, for example 50 million/ml. This is measured by counting the number of sperm on a grid under the microscope in a tiny drop which represents the rest of the sample.

A normal sperm concentration is at least 15 million/ml.

A low sperm count is known as oligozoospermia, a very low sperm count is known as cryptozoospermia and no sperm whatsoever is known as azoospermia.

The image on the left shows azoospermia where there are no sperm and only small bits of cell debris. The image on the right is a normal sample.

Men with a slightly reduced sperm count may still be able to get pregnant naturally, although it may take longer than expected. However, men with a very low sperm count will mostly likely need IVF treatment using a method of insemination called ICSI where sperm are injected directly into the egg. It only requires one healthy sperm for each egg so ICSI is even effective for men with severely low sperm counts.

Common causes of low sperm count:

  • Hormone imbalance
  • Recent illness, particularly infection or fever
  • Excessive drug or alcohol consumption
  • Certain genetic conditions such as cystic fibrosis
  • Anabolic steroid use
  • STDs
  • Frequent overheating of the testes eg. hot tubs or cycling
  • Obesity

Sperm motility

Sperm motility is a measure of how well the sperm swim. They are classified as either progressive if they swim well, non-progressive if they are alive but not swimming, or immotile if they cannot swim (usually because they are dead). It is normal to have a mixture of all these types of sperm in a healthy sample but at least 32% should be swimming strongly to have a good chance of fertilizing an egg successfully.

Less than 32% motility is considered abnormal and is known as asthenozoospermia. Poor sperm motility will definitely limit your chance of getting pregnant naturally and will also mean you need to have ICSI treatment if you are having IVF.

Sometimes sperm can be described as ‘sluggish’ which means that they are progressively motile ie. swimming in straight lines, but they are moving more slowly than they should be. This will make it much more difficult for the sperm to reach the egg in a natural pregnancy, but it is easily overcome in the lab for IVF treatment and you may be recommended to have ICSI.

Sperm morphology

Sperm morphology measures the percentage of sperm which look normal. It is an important result because each part of the sperm plays a vital role so it is essential that there are a good number with all their functional parts. For example, the sperm’s DNA is tightly packed into the head so this area needs to be perfectly formed to create a healthy embryo.

Sperm production is unusual because it is normal for the vast majority of sperm have some sort of defect. Having only 4% sperm with correct morphology is considered healthy and it is rare to see more than 10% normal morphology. Luckily the testes make thousands of sperm every second to ensure there are enough normal ones in every sample. Low morphology less than 4% is reported as teratozoospermia.

Low sperm morphology (<4%) has minimal impact on a man’s fertility as long as the morphology isn’t 0% (100% abnormal sperm). You may still be recommended to use ICSI if you are having IVF treatment to give the best chance of good fertilization.

Specialist, advanced tests

Some clinics offer additional tests alongside a routine semen analysis which can help to investigate how healthy the sperm are and how likely they are to make a healthy pregnancy:

  • Oxidative stress test – oxidative stress is the main cause of DNA damage in sperm; it can cause poor sperm function and reduced IVF outcomes
  • DNA fragmentation testing – looks for breaks in the sperm DNA which have been linked to reduced IVF outcomes and miscarriage
  • Sperm binding tests – measures the sperm’s ability to bind to the egg which is essential for natural fertilization
  • Hyaluronan binding test – sperm which can bind to a substance called hyaluronan are thought to be healthier and more mature
  • Mixed antiglobulin reaction – detects antibodies which stop sperm swimming and functioning normally

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