Causes of Infertility

What are the main causes of female infertility? What are the main causes of female infertility?

What are the causes of infertility?

There can be many reasons why couples struggle to conceive. Male factor infertility accounts for roughly 30% of these cases, while female factor infertility also accounts for another 30%. However, there are some cases where it may not be possible to identify a precise medical cause of the fertility issue, in which the problem is unknown. It is estimated 1 in 4 couples will suffer from an unknown fertility issue.

For women, the most common causes of infertility are:

  • Ovulation disorders: Disorders which stop or disrupt ovulation (the release of an egg each month from the ovaries), such as polycystic ovary syndrome (PCOS), can make it difficult to get pregnant.
  • Age: From the age of 35, fertility begins to decrease naturally at a quicker pace. From the age of 40, there is a less than 10% chance of getting pregnant naturally.
  • Endometriosis: A chronic condition where cells that are usually found within the womb lining grow outside the womb, which depending on its severity can cause varying degrees of infertility.
  • Fibroids: Larger fibroids can reduce fertility by causing blockages or distortions.
  • Sexually transmitted infections: Left untreated, certain sexually transmitted infections can cause pelvic inflammatory disease (PID) and lead to infertility.
  • Chronic diseases: Conditions such as diabetes, cancer, thyroid disease, asthma or depression have all been linked to fertility problems.
  • Specific medication: Medication used to treat specific conditions, such as antidepressants, can have an impact on fertility.


For men, the most common causes infertility are:

  • Genital tract disorders
  • Erectile dysfunction
  • Reduced sperm count and motility of the sperm
  • High BMI and obesity
  • Undescended testicles
  • Physical trauma or surgery to the testicles


  • Infertility in men (30%): alterations in the testicular area, obstruction of tubes, prostate pathologies, problems with ejaculation or erectile function, or changes in the semen.
  • Infertility in women (30%): early menopause, endometriosis, obstructions or lesions in the fallopian tubes, uterine or cervical anomalies, or ovulation problems.
  • Mixed or combined causes (20%).
  • Unexplained causes (20%).

What are the main causes of male infertility?

What are the main causes of female infertility?

What type of injuries affects the fallopian tubes?

Around 25% of cases of female infertility are due to blockage of the fallopian tubes. Normally the fallopian tubes pick up the egg as it is released during ovulation. The sperm fertilizes the egg in the fallopian tubes. Damaged or obstructed fallopian prevent this movement so fertilisation cannot take place. Fallopian tubes can be damaged by:

  • Pelvic infections caused by sexually transmitted diseases such as Chlamydia or Gonorrhea Previous surgery, including appendectomy which may then cause scar tissue and adhesions within the pelvis.
  • Previous history of ectopic pregnancy where a pregnancy implants in the fallopian tube.

What is endometriosis and how many women are affected by it?

There is a strong relationship between endometriosis and sub fertility. While some 10% of women suffer from the disease, this rises to 35% for women with fertility problems.

The disease gets its name from the word endometrium, which is the tissue that lines the inside of the uterus and which is shed each month during menstruation. Endometriosis is caused by the presence of this tissue in places other than the uterus.It is most frequently found in the ovaries, fallopian tubes, the ligaments which support the uterus and the lining of the pelvic or abdominal cavity. This tissue is sensitive to the hormonal changes that occur during menstruation, the source of the symptoms associated with the disease. Although some patients may not have any symptoms, the most common ones are pain and infertility. Pain may only occur during menstruation, but there can also be gastrointestinal and urinary symptoms, if endometrial tissue invades other areas such as the intestine, the bladder or the colon.

Infertility related to endometriosis can arise from the changes which occur in the pelvic anatomy of patients during their menstrual cycles. It can cause obstruction of the tubes or the formation of ovarian cysts, which sometimes require surgery and so result in the loss of ovarian tissue and decreased fertility. There are medical and surgical treatments available and in many cases becoming pregnant can check the progress of the disease.

How is endometriosis detected?

Endometriosis is usually diagnosed by undergoing a surgical procedure called a laparoscopy. If endometriosis is present in the ovaries it can be sometimes be detected using ultrasound. Ovarian cysts caused by endometriosis are known as a chocolate cysts or endometriomas.

Can you start fertility treatment without having surgery in cases of severe endometriosis?

Whether or not surgery is essential before fertility treatment is something that you will need to discuss with your gynaecologist. It will depend on the size of the chocolate cysts and your ovarian reserve and on the response capacity of the affected ovary. IVF is an appropriate treatment for fertility associated with endometriosis when other techniques have not been successful.

There is a common belief that pregnancy can cure endometriosis. This is not true, but during pregnancy the symptoms of endometriosis may be temporarily suppressed.

What are polycystic ovaries?

Around 20% of women have polycystic ovaries (PCO). The term refers to the increase in the number of small cysts (antral follicles) on the surface of the ovary. These can be detected with an ultrasound scan. There are a great many women with PCO who have no problems ovulating and getting pregnant. However, some women who have this characteristic ultrasound scan pattern also have the condition known as Polycystic Ovarian Syndrome (PCOS). These women have irregular menstrual cycles or even a lack of menstruation and have problems getting pregnant.

Why does anovulation happen?

Anovulation is when the ovaries fail to produce, mature or release an egg.

Factors that can contribute to anovulation include: stress, significant weight gain or loss, excessive production of prolactin (the hormone responsible for producing breast milk) and polycystic ovaries. Approximately 35% of women experience anovulation at some time during their lives. The origin of this hormonal disorder may be in the hypothalamus, a part of the brain that controls hormonal function, the pituitary gland, or in the ovary itself.

How is male infertility analysed?

To study male fertility, the number, motility and shape of the spermatozoa are analysed. The World Health Organization (WHO) reference values for a normal semen analysis is a sperm count of at least 15 million sperm per ml, with at least 32% of the sperm having progressive motility and at least 4% having a normal shape. If the sperm count or motility is lower than this the chances of a pregnancy occurring naturally is reduced.

What are the causes of a low sperm count?

The main causes of a low sperm count are: problems in the glands in the brain (the pituitary gland and the hypothalamus) which produce the hormones regulating the formation of spermatozoa; genetic disorders (Klinefelter syndrome, alteration of the genes on the Y-chromosome that regulate the formation of spermatozoa, etc.); or various testicular problems such as lack of development, anomalous development, failure to descend into the scrotum, etc.

What kind of abnormalities can occur in sperm?

Spermatozoa can show anomalies in their motility (astenozoospermia), shape (teratozoospermia) or vitality (necrozoospermia).

What are the main causes of abnormalities in sperm?

  • Infections or the presence of antibodies.
  • Alterations in the number of chromosomes; DNA fragmentation; oxidation phenomena; varicocele, etc.
  • Diabetes, thyroid disorders, kidney disease, certain medications, drugs, tobacco and stress.

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