11 October 2019

What are the most common causes of infertility?

Medical Director
Cesar Diaz-Garcia
MD PhD Assoc Prof
IVI London


According to the National Institute for Health and Care Excellence (NICE), one in seven heterosexual couples in the UK is affected by infertility. They also note that since their original guidelines on fertility were published in 2004, there has been an increase in fertility problems, and more people are seeking help and treatment. In Europe more widely, birth rate statistics have shown a fall for generations. While this may be due to social factors, it is also partly caused by infertility.

The most common causes of infertility are associated with approximately 30% male fertility factors as a result of poor quality sperm, 30% female fertility factors arising from ovulatory problems and the remaining 40% are a combination of factors or unexplained. In this article we take a look at the main causes of infertility for both men and women and how these can be treated.

The most common causes of infertility for women

For women, problems with ovulation, the monthly release of an egg as part of the menstrual cycle, is the main cause of infertility. Some conditions completely prevent the release of an egg, and others can result in inconsistent ovulation. Specific causes, roughly in order of prevalence, are:

PCOS is the most common ovulation disorder, were there exists an imbalance of hormones that causes a disruption to the whole cycle, leading to irregular or even completely absent periods. One of the main features of this condition is the presence of a multiple number of follicles . The NHS estimates that this condition affects about one in five women in the UK, many of whom remain undiagnosed because they are symptom free, apart from having difficulty in getting pregnant.

  • Advanced maternal age

The ageing process is one of the main causes of infertility in developed countries, leading to a lower ovarian reserve and a poorer egg quality. As a result, not only pregnancy rates decrease but also miscarriage rates are higher. All these factors combined, lead to lower live birth rates.

Endometriosis is an often painful condition in which the tissue lining the uterus starts to develop outside the womb, in places such as the ovaries, fallopian tubes or the outside of the uterus. There has been found a correlation between infertility and endometriosis, probably due to a poorer egg quality in women suffering from this condition. Nonetheless, the presence of endometriosis does not necessarily mean that women will always be infertile.

  • Other causes

Other causes of infertility in women include fibroids, pelvic inflammatory disease and certain medications, for example chemotherapy treatment.

What are the main causes of infertility in men?

For men, infertility generally stems from issues with the quality or quantity of sperm. These could be a result of testicular damage or problems with the delivery of sperm due to ejaculatory, obstructive or secretory disorders.

  • Quality and quantity of sperm

Poor sperm quality can mean that sperm has low motility or an abnormal shape, making it more difficult for the sperm to move and to reach the egg. A low quantity of sperm, where the semen contains few or even no sperm, also has an obvious impact on fertility.

  • Testicular damage

Damage to the testicles can affect the sperm, for example by overheating as a result of too much sitting down or over-tight underwear. Damage can also be caused by trauma resulting from sport, testicular surgery or infection, or a congenital defect such as undescended testicles.

  • Ejaculatory or sperm production disorders

Problems with ejaculation can include premature or retrograde ejaculation or failure to ejaculate. These have an impact on fertility due to the sperm’s inability to reach the egg. Furthermore, sperm production disorders also affect men. These problems can be central (signalling to activate the sperm production) or peripheral (lack of production of sperm in the testicles)

Other lifestyle factors can affect both men and women

Both ovulation and the production of healthy sperm can also be affected by environmental factors and lifestyle choices. These include:

  • Age: for women and to a lesser extent for men, fertility declines with age. For women, this decrease starts in the mid-30s and tapers off completely at menopause.
  • Being overweight: a BMI of 30 or more reduces fertility for both sexes and for women, being very underweight can also affect ovulation. Obesity has also an impact in ART success rates and increases the risk of complications during the pregnancy for both mum and baby.
  • Infections: chlamydia and other sexually transmitted infections can reduce fertility.
  • Smoking: smoking reduces semen quality and a woman’s chance of conceiving. It is also dangerous if conception does take place. See more in our article about the impact of smoking during preconception.
  • Alcohol consumption and that of other recreational drugs can both affect fertility and pose danger to a developing foetus.
  • Exposure to environmental hazards and industrial toxins such as pesticides and solvents can be damaging, as are some medications such as anabolic steroids and corticosteroids. You should always discuss the implications of any prescription medication with your GP if you are trying to get pregnant.

You are experiencing infertility: what next?

If you’ve been trying to conceive for a year, or for women over 35 for six months, without success, it’s time to seek help. Happily, there are various treatment options available. For example:

  • Intrauterine insemination (IUI) to treat minor problems. Artificial insemination is the least invasive fertility treatment, were the ovarian cycle is monitored to ensure when ovulation takes place, followed by depositing a prepared semen sample inside the patient’s uterus. Have a look at what’s involved in our IVI video about IUI.

  • In Vitro Fertilisation (IVF), recommended where there is a need for fertilisation and selection of a healthy embryo in the laboratory, is the best-known assisted reproduction technique. It is recommended where previous simpler treatments have failed, or for long term infertility, woman with endometriosis, fallopian tube injury or for severe male factor infertility.



  • The use of donor eggs or sperm for cases where there are irreversible problems with the production of either eggs or sperm. Different regulations apply for egg donation treatment in the UK and Spain. As a result, anonymity and waiting times might differ when doing an egg donation treatment in the UK or one of our IVI clinics in Spain.

Some authorities include waiting to try for pregnancy, and consequently delaying seeking help if there are problems, as one of the primary causes of infertility. Since egg quality declines with age, even at a time when ovulation is still taking place, the chances of a successful pregnancy steadily reduce.

So, it is a good idea to take action sooner rather than later. If you would like more information, don’t hesitate to get in touch with us at IVI.

Request more information, no obligation

Comments are closed here.

Back to toparrow_drop_up