Causes of Low Sperm Count and Motility

Sperm approaching an ovum

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One of the primary causes of infertility is low sperm count and motility. These issues, coupled with poor sperm quality, represent 90% of all cases of infertility in men and anywhere from 20% to 40% in couples.

Nearly one in six men are affected by infertility related to problems with their sperm. The causes can range from hereditary factors and lifestyle choices to past infections and a person's age.

The term for low sperm count and motility is oligoasthenoteratozoospermia (OAT).

Low Sperm Count and Motility

The term oligoasthenoteratozoospermia, or OAT, is used when all three of the following factors are present:

  • An abnormally low level of sperm of a healthy shape (teratozoospermia)
  • An abnormally low amount of sperm (oligozoospermia)
  • An abnormally low amount of sperm with good motility (asthenozoospermia)

Idiopathic oligoasthenoteratozoospermia is used when the cause of the condition is unclear. Up to 30% of male infertility cases are said to have idiopathic OAT.

Causes and Treatment of OAT

The factors for OAT can be broadly broken down into four categories: genetic factors, lifestyle factors, testicular factors, and testicular/ejaculatory dysfunction.


Genetic factors can affect every stage of male fertility—from DNA damage in sperm cells (spermatozoa), genetic defects of the Y chromosome, and genetic disorders like Klinefelter syndrome.

While most genetic factors are not treatable, they can often be overcome with the use of in vitro fertilization (IVF).


Lifestyle factors involve both habits and conditions that directly affect the sperm. Many of these factors can be changed and doing so can significantly improve a man's chance of conceiving.

Lifestyle factors that can affect sperm help include:

  • Alcohol consumption: As few as five drinks per week can significantly lower testosterone levels and sperm qualities. Many recreational drugs have the same effect.
  • Certain medications: Prescription drugs can also affect the quality of sperm, including anabolic steroids and Tagamet (which is used to treat stomach acid). Others can affect sperm motility, such as Azulfidine used to treat rheumatoid arthritis and Macrobid used to treat bladder infections.
  • Heat: Overheating the testes is associated with low sperm count. Causes include too hot showers baths, or sauna, as well as wearing tight briefs instead of boxers. Overexertion at the gym can also have the same effect.
  • Smoking: Smoking is strongly linked to male infertility although the reasons are not entirely clear. Smoking can reduce the sperm count by 17.5% and sperm motility by 16.6%.
  • Strenuous activities: Riding (cycling, horseback) can cause testicular inflammation. This can be relieved by simply taking a break from the activity.
  • Weight: Obesity is known to cause hormonal changes that can directly impact fertility. Being underweight can also have a negative effect.

Testicular Factors

Testicular factors interfere with the testicle's ability to produce ample quantity or quality of sperm. Some of the factors can be treated but others cannot.

Examples of testicular factors include:

  • Certain past infections (syphilis, mumps, malaria) that are known to either directly or indirectly affect the male reproductive system)
  • Chemotherapy and radiation therapy
  • Enlargement of the varicocele (which can be often be treated surgically and non-surgically)
  • Older age
  • Testicular cancer
  • Testicular trauma

Testicular and Ejaculatory Dysfunction

Testicular and ejaculatory dysfunction refers to any condition that impedes the ability to ejaculate or obstructs the flow of semen in the male genital tract. These factors include:

  • Erectile dysfunction (which can often be treated with medication)
  • Hypospadias, a congenital defect in which the opening of the urethra is not situated on the head of the penis
  • Impotence by other causes
  • Obstruction of the vas deferens or ejaculatory duct
  • Prostatitis (inflammation of the prostate gland)
  • Retrograde ejaculation where semen is inadvertently redirected to the bladder

A Word From Verywell

Many of the causes of male infertility can be treated. Even when they cannot be treated, there is an array of assisted reproductive procedures that can improve a couple's chance of conceiving. They include fertility drugs, medical devices, surgery, or a combination of treatments. 

If you are experiencing male infertility, speak with a fertility specialist. Whatever the cause, they might be able to help.

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