Common causes of infertility

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This article outlines the most common causes of infertility in New Zealand. Causes of infertility can be related to the woman, the man, or both.

What is infertility?

There are several definitions of infertility. The general understanding of the word is that despite regular sexual intercourse, without any form of contraception, a couple are unable to conceive a baby. The time period quoted will vary depending upon where you are getting your information.

If you are under 35 years and both healthy, the majority of couples will successfully become pregnant in less than 2 years. The National Institute for Health and Clinical Excellence (NICE) in the UK defines infertility as –

‘failure to conceive a pregnancy after regular unprotected sexual intercourse for two years in the absence of known reproductive pathology’.

Other sources, however, do define infertility as the inability to become pregnant after 1 year.

If a couple believe they are having problems conceiving a baby they should seek support and advice at any time.

Causes of Infertility

There are many different causes of infertility – and in fact there are so many possible factors that can go wrong from the moment of sexual intercourse to the next menstrual period being due, that it can seem a miracle that anyone does get pregnant!

In 35% of cases of infertility a cause will be found with the woman; in 35% of cases a cause will be found with the man; in approximately 20% of couples there may be a problem found in the man and the woman and in the remaining 10% of cases no problem will be found and yet infertility persists.

Female causes of infertility

Endometriosis

This is a common cause of infertility among women. The endometrium is the medical term for the lining that grows inside the womb and is shed every month during menstrual periods.

This endometrial tissue can grow outside the womb and this is known as endometriosis, which sometimes causes:

  • possible infertility by damaging the ovaries or fallopian tubes
  • heavy painful periods
  • irregular bleeding
  • repeated miscarriages.

Ovulation problems

Various conditions can affect the production and release of an egg form the woman’s ovaries during the menstrual cycle. Symptoms that could alert the possibility of this include:

  • Absent or irregular periods
  • Light bleeding
  • Excessively heavy bleeding (needing to change pads or tampons more frequently than every 2-3 hours).

The egg itself

The egg the woman produces may be poor quality and there are no symptoms that would alert the couple to this possibility.

If the egg is damaged or has a chromosomal abnormality it may not result in a pregnancy. This is more common as the woman gets older (over 35).

Polycystic ovary syndrome

As a result of small cysts on the ovaries, there is an imbalance of the female hormones and the woman does not ovulate regularly. Symptoms of this condition include:

  • Irregular periods
  • Acne
  • Being overweight
  • Unusual hair growth on the face, for example.

Blocked tubes in the female reproductive system

A successful pregnancy depends upon the sperm being able to reach the egg and the fertilised egg reaching the womb, to implant safely in the wall of the womb. If there are blockages in the fallopian tubes, the chances of a successful pregnancy will be greatly impeded. Common causes are:

  • pelvic inflammatory disease
  • sexually transmitted infections, such as clamydia
  • infection from a previous birth
  • blockages from previous surgery (following ectopic pregnancy or sterilisation procedures).

Usually the woman would not be aware of blocked fallopian tubes.

Male causes of infertility

Blocked tubes in the male reproductive system

Sperm is made in the testicles and moves along the vas deferens to the urethra during ejaculation. If there is a blockage in the epididymus in the testicles or the vas deferens then sperm will not be able to leave the penis during sexual intercourse. Obstruction may occur due to sexually transmitted infections, or varicose veins in the testicles, known as varicoceles. Blocked tubes do not have any symptoms, so you won’t be aware that this is the case until tests are done.

Problems with spermatozoa – or sperm

  • Sperm may be absent
  • Sperm may be reduced – there is an amazingly large number of sperm in each ejaculate, with the World Health Organisation (WHO) recommending that a normal ejaculate contains at least 40 million spermatozoa!
  • Sperm may not move well – known as poor motility (50% of sperm should be moving forwards)
  • Sperm may be abnormally shaped

There are no symptoms with sperm problems, so you won’t be aware that this is the case until tests are done.

Allergy to sperm

Men may have an immune reaction to sperm cells – producing antibodies which kill the sperm. This is more common after a vasectomy.

There is controversy surrounding these diagnoses.

Combination Infertility

In approximately 10-20% of couples both partners have a problem which is contributing to infertility. This term is also used if the man or woman has more than one problem.

Unexplained infertility (UI)

Many couples (approximately 10%) endure endless fertility tests, but no problem is ever found with either partner.  It is possible that factors such as:

  • being under weight
  • being over weight
  • environmental factors, such as exposure to leads or pesticides

– may contribute to this.

There are other causes of infertility in men and women, only the common causes are outlined in this article. Please speak to your doctor regarding your own individual circumstances.

Research continues to find other possible causes of infertility.

Some useful articles and resources on infertility

We have more information on Increasing Your Chances of Getting Pregnant. You can also found out more about the Causes of Infertility. And here we talk about the Treatments for Infertility.

Investigating Infertility explains the most common investigations that couples undergo when they’re experiencing infertility.

Find out more about fertility hypnosis or Chinese medicine treatments.

Paula Skelton

Paula Skelton is a qualified NZ nurse and midwife, a midwifery & childbirth educator and the mum of three lovely girls.

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