Sperm Morphology – What is it & How Does it Affect Fertility

January 25, 2023
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When a couple faces difficulty in getting pregnant or having a successful pregnancy, a fertility specialist will check both partners. They will check the overall health and the health of the reproductive organs of both males and females. When it comes to the male partner, sperm morphology is very important for a successful pregnancy – be it natural or through fertility treatments.

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What is Sperm Morphology?

The sperm has a particular shape and size to help it travel fast and penetrate the egg, thus fertilizing it. As per studies, you can find around 39 million sperm per ejaculation. Among these millions of sperms, many will be irregular in shape or size, without a proper head or length. That is ok.

It takes just one sperm to fertilize an egg. For this one sperm to reach and fertilize successfully, millions of sperm travel up the fallopian tube, and the strongest of them all succeeds. So, out of these millions of sperm, you need just a small percentage to be of the right shape and size, in other words, the right sperm morphology for a successful pregnancy.

When a couple is having difficulty conceiving, a routine semen analysis will help understand sperm morphology. A sample of semen is studied closely under a microscope to understand the morphology. A healthy sperm must have an oval-shaped head and a midpiece and a tail.

If this head does not have a proper shape or if there is no tail, then the sperm is abnormally formed. The lack of a proper head will affect the sperm’s ability to penetrate the egg for fertilization. The lack of a tail will affect its ability to swim up the fallopian tubes, to reach the egg.

Sperm Morphology Range

The required sperm morphology normal range is about 4 - 14% only. Yes, you read that right. You need just around 14% of the sperm to be of the right shape and size for a successful pregnancy.

When sperm morphology is above 14%, according to Kruger criteria, the probability of fertility is very high. If it is below 4%, meaning the percentage of healthy sperm is less than 4%, it is an abnormal sperm morphology, which can take longer to achieve pregnancy. The WHO also recommends a similar range.

Your fertility doctor can help identify the reason behind the abnormal sperm morphology and help rectify it with suitable treatments.

Reasons for Abnormal Sperm Morphology

Every male will have a certain percentage of abnormally formed sperm. The range will vary from person to person depending on the following factors:

  • Testicular Temperature – Higher your testicles’ exposure to heat, the higher the chances of abnormal sperm.
  • Chemical Exposures – If you are constantly exposed to chemicals due to your work or the environment you live in, it can result in a higher range of abnormal sperm morphology
  • Infections – Infections when left untreated can affect the sperm shape and quality.
  • Genetics – Abnormal sperm morphology can be a genetic trait too. Unless a person tests their semen sample, abnormal sperm morphology will g,o unnoticed. So this can be tricky to identify.

Types of Sperm Morphology

Let’s take a deeper look into sperm morphology to understand how it can differ and which can cause fertility issues. A normal sperm morphology should have an oval head, an intact middle piece, and a tail that does not coil. Abnormal sperm can be as follows:

1. Macrocephaly

  • The sperm head is bigger than normal
  • Head carries extra chromosomes
  • Sperm might have trouble fertilizing an egg
  • Could be genetic

2. Microcephaly

  • Sperm head is smaller than normal
  • Sperm might have defective acrosome
  • Might have lesser genetic material

3. Pinhead Sperm

  • The sperm head appears like a pin
  • Might contain very little or no DNA material
  • Might indicate diabetes

4. Tapered Head Sperm

  • The sperm head is shaped like a cigar
  • Indicates a possibility of Varicocele
  • This could be due to constant scrotum exposure to heat
  • The head might contain abnormal chromatin
  • The head might contain abnormal packaging of the DNA material
  • Chances of an abnormal number of sperm chromosomes called aneuploidy

5. Thin Narrow Head Sperm

  • Very rare
  • A variation of the tapered-head sperm
  • This could be due to broken DNA material, Varicocele, or disruption in the head formation

6. Globozoospermia

  • Sperm will be round-headed instead of oval
  • Indicates an absence of acrosome or important parts of the head
  • Sperm can break down prematurely

7. Headless Sperm

  • Known as acephalic or decapitated sperm
  • Has no head, genetic material, or chromosomes

8. Tail-Less Sperm

  • Known as acaudate sperm
  • Seen during the death of most cells in an organ

9. Nuclear Vacuoles

  • The sperm head has two or more large vacuoles (bubbles that look like cysts)
  • Has multiple small vacuoles in the head
  • Might have low potential for fertilization

10. Multi-Head Sperm

  • Sperm has multiple heads or tails
  • This could happen due to heavy exposure to chemicals, toxins or high prolactin in the blood.

11. Coiled Tail Sperm

  • Damages in tail
  • Sperm cannot swim well
  • Indicates the presence of bacteria
  • Could be due to heavy smoking

12. Stump Tail Sperm

  • Tails are short, leading to low motility or movement
  • Could be due to the late formation of sperm in the testicles
  • Is an autosomal genetic disease

13. Swollen Mid-Piece

  • The sperm neckpiece will be swollen
  • Indicates defective mitochondria
  • The guidance system to move the chromosomes from the sperm's neck might be broken or missing.

Must Read : How to increase sperm count and motility?

How to Improve Sperm Morphology?

When you have low sperm morphology, you want to know how to increase sperm morphology. Here are a few tips to improve sperm morphology:

  • Wear loose-fitting underwear
  • Avoid self-medication
  • Avoid steroids, tobacco, and alcohol
  • Avoid hot tubs or constant exposure of the testicles to heat
  • Exercise regularly and follow a healthy diet rich in antioxidants
  • If overweight, then lose weight with guidance

Can Abnormal Sperm Morphology Cause Birth Defects?

Unless the sperm head is carrying defective genes or broken DNA, the sperm morphology won’t cause any birth defects. Birth defects are mostly due to damage in the DNA package and it can be from either partner. Abnormal sperm morphology will make it difficult to conceive but may not cause any defects in the baby.


How to Correct Sperm Morphology?

Simple changes to lifestyle and diet can have a big impact on your sperm health and morphology. In case of abnormal sperm morphology, a fertility specialist can help identify the exact problem and help rectify it.