What Causes Infertility?

Risk Factors of Infertility

  • Age – a woman’s fertility starts to drop after she is about 32 years old, and continues doing so.
  • Smoking – smoking significantly increases the risk of infertility in both men and women. Smoking may also undermine the effects of fertility treatment.
  • Alcohol consumption – a woman’s pregnancy can be seriously affected by any amount of alcohol consumption. Alcohol abuse may lower male fertility.
  • Being obese or overweight – in industrialized countries overweight/obesity and a sedentary lifestyle are often found to be the principal causes of female infertility. An overweight man has a higher risk of having abnormal sperm.
  • Over-exercising – may lead to ovulation problems.
  • Not exercising – leading a sedentary lifestyle is sometimes linked to lower fertility in both men and women.
  • Sexually transmitted infections (STIs).
  • Exposure to some chemicals – some pesticides, herbicides, metals (lead) and solvents have been linked to fertility problems in both men and women.
  • Mental stress – studies indicate that female ovulation and sperm production may be affected by mental stress. If at least one partner is stressed it is possible that the frequency of sexual intercourse is less, resulting in a lower chance of conception.

Causes of Infertility

There are many possible causes of infertility. Unfortunately, in about one-third of cases no cause is ever identified.

Causes of infertility in women

  1. Ovulation disorders – problems with ovulation are the most common cause of infertility in women, experts say. Ovulation is the monthly release of an egg. Ovulation disorders can be due to: 
    • Premature ovarian failure – the woman’s ovaries stop working before she is 40.
    • PCOS (polycystic ovary syndrome) – the woman’s ovaries function abnormally. She also has abnormally high levels of androgen. About 5% to 10% of women of reproductive age are affected to some degree.
    • Hyperprolactinemia – if prolactin levels are high and the woman is not pregnant or breastfeeding, it may affect ovulation and fertility.
    • Poor egg quality and quantity- eggs that are damaged or develop genetic abnormalities cannot sustain a pregnancy. The older a woman is the higher the risk.
    • Thyroid abnormality
  1. Problems in the uterus or fallopian tubesThe egg travels from the ovary to the uterus (womb) where the fertilized egg grows. If there is something wrong in the uterus or the fallopian tubes the woman may not be able to conceive naturally. This may be due to:
    • Surgery – pelvic surgery can sometimes cause scarring or damage to the fallopian tubes. Uterine and cervical surgery may cause anatomical problem.
    • Submucosal fibroids – benign or non-cancerous tumors found in the muscular wall of the uterus. They may interfere with implantation. They can also block the fallopian tube, preventing sperm from fertilizing the egg.
    • Endometriosis – cells that are normally found within the lining of the uterus start growing elsewhere in the body.
  2. Medications – some drugs can affect the fertility of a woman. These include: 
    • NSAIDs .
    • Chemotherapy .
  3. Radiotherapy .

Causes of infertility in men


Abnormal semen is responsible for about most of the cases of male infertility. Unfortunately, in many cases doctors never find out why. The following semen problems are possible:

  • Low sperm count (low concentration) – the man ejaculates a lower number of sperm, compared to other men. Sperm concentration should be 15 million sperm per milliliter of semen.
  • No sperm – when the man ejaculates there is no sperm in the semen
  • Low sperm mobility (motility) – the sperm cannot “swim” as well as it should.
  • Abnormal sperm – perhaps the sperm has an unusual shape, making it more difficult to move and fertilize an egg.

Sperm must be the right shape and able to travel rapidly and accurately towards the egg. If the sperm’s morphology (structure) and motility (movement) are wrong it is less likely to be able to reach the egg and fertilize it. 

The following may cause semen to be abnormal:

  1. Testicular infection
  2. Testicular cancer
  3. Testicular surgery
  4. Overheating the testicles – frequent saunas, hot tubs, very hot baths, or working in extremely hot environments can raise the temperature of the testicles. Tight clothing may have the same effect on some people.
  5. Ejaculation disorders – for some men it may be difficult to ejaculate properly. Men with retrograde ejaculation ejaculate semen into the bladder.
  6. Varicocele – this is a dilated vien in the scrotum that may cause the sperm to overheat.
  7. Undescended testicle – one (or both) testicle fails to descend from the abdomen into the scrotum during fetal development. Sperm production is affected because the testicle is not in the scrotum and is at a higher temperature.
  8. Hypogonadism – Testosterone deficiency can result in a disorder of the testicles.
  9. Genetic abnormality 
  10. Mumps – this viral infection usually affects young children. However, if it occurs after puberty, inflammation of the testicles may affect sperm production.
  11. Hypospadias – the urethral opening is at the underside of the penis, instead of its tip and there is difficulty in reaching the cervix.
  12. Cystic fibrosis – These men have a missing or obstructed vas deferens (tube connecting the testes to the urethra; it carries sperm from the epididymis to the ejaculatory duct and the urethra).
  13. Radiotherapy – Radiation therapy can impair sperm production.
  14. Medications
  • Sulfasalazine 
  • Anabolic steroids
  • Chemotherapy

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