The 3 Most Common Causes of Infertility

Infertility can originate in both members of the couple, so its study involves ruling out both male and female conditions.
The 3 Most Common Causes of Infertility
Mariel Alexandra Mendoza Delgado

Written and verified by Mariel Alexandra Mendoza Delgado.

Last update: 01 February, 2023

Infertility, from a clinical point of view, refers to the inability to achieve a pregnancy after 12 months of regular unprotected intercourse. This condition affects about 15-20% of couples of reproductive age. So, what are the most common causes of infertility?

Fertility is usually analyzed only from the woman’s point of view. However, this shouldn’t be the case, as it’s a health problem for both people in the relationship, and, regardless of who is carrying the dysfunction that prevents pregnancy (and it could be both of them), the situation will affect them both.

The increase in the prevalence of infertility is related to a delay in the desire to become a mother (older age in women), a decrease in semen quality, lifestyle, and exposure to various environmental factors (smoking and alcoholic habits).

Factors associated with infertility

During the study of an infertile couple, different factors have been found present:

  • Ovulatory, which is from development to follicular maturation and the release of the ovum, and is present about 20% of the time.
  • Utero-tubal-peritoneal, which has to do with the anatomical integrity of the structures involved in pregnancy and involves the presence of pelvic adhesions, and occurs in about 30% of couples.
  • Sperm migration – semen migration disorders that include disorders associated with cervical mucus and sperm motility, and are present in 10% of cases.
  • Alterations in the quality and quantity in the sperm sample, which can occur in around 30% of cases.
  • And, finally, in between 10 and 15% of couples, the infertility can’t be explained).

Having said this, about 40% of all infertile couples usually have a combination of factors. The most frequent causes of infertility, both in men and women, are broken down below.

Most frequent causes of infertility in women

1. Inability to ovulate

Infertility due to ovulatory problems.
Ovulation problems continue to represent the main cause of female infertility.

The inability to ovulate, known as anovulation, is the cause of female infertility in up to 40% of cases. It influences from development to follicular rupture and the release of the oocyte.

Causes of the inability to ovulate include premature ovarian failure, primary ovarian failure, polycystic ovary syndrome, hyperprolactinemia, functional hypothalamic anovulation, aging, thyroid disease, body weight disturbances, and various bodily factors.

Polycystic ovary syndrome

Polycystic ovary syndrome affects up to 10% of women of reproductive age and is considered responsible for around 80% of anovulatory infertility cases.

It is characterized, in addition to anovulation, by irregular or absent and painful menstrual cycles, a tendency to be overweight/obese, hyperandrogenism (manifested by acne and hirsutism), and in most cases, hyperinsulinemia.

For the diagnosis of polycystic ovary syndrome, the presence of at least two of three of the following findings is required:

  • Signs or symptoms of hyperandrogenism: hair loss, acne, increased facial or body hair in unusual areas, and increased levels of testosterone in the blood.
  • Irregular or absent menstrual cycles.
  • The presence of polycystic ovaries on ultrasound.

Treatment is aimed at improving lifestyle, combining a good diet and exercise with weight loss. Sometimes to correct insulin resistance, insulin sensitizers such as metformin are used, which also helps to improve hyperandrogenism.


Infertility is also associated with the aging of women. As age increases, there is aging of the ovary with a decrease in the quality of the ovules and a decrease in the ovarian reserve, as well as an increase in medical conditions that alter the endocrine pattern.

The quality of the ovules is fundamentally seen in alterations in the processes of cell division, so there’s a greater risk of chromosomal alterations that prevent the pregnancy from reaching term.

Excess weight or obesity

The excess of adipose tissue produces an increase in the concentrations of the hormone leptin that causes dysregulation of the hypothalamic-pituitary-gonadal axis. In women, this causes infertility due to an increase in testosterone and a decrease in estrogen and progesterone.

In another order, this is related to hyperinsulinism and insulin resistance that causes the release of androgens by the ovaries, and a decrease in sex hormone-binding globulins.

2. Genital infections

Genital infections as causes of infertility in women figure on this list because they cause tubal-peritoneal damage. Although there are many sexually transmitted diseases that can be linked to infertility, two infections prevail among all: Neisseria gonorrhoea and Chlamydia trachomatis.

Chronic genital infections cause pelvic inflammatory disease that damages the uterus and fallopian tubes. It also causes the presence of pelvic adhesions that can cause infertility, chronic pelvic pain, and an increased risk of ectopic pregnancy.

3. Endometriosis

Endometriosis can produce infertility because ovarian and tubal function is altered. It’s the presence of endometrial (uterine) tissue outside the uterine cavity. This is associated with anatomical distortions that limit the mobility of the uterine fimbriae or obstruct the tubes.

It causes long, painful and abundant menstrual cycles, as well as pelvic pain not related to menstruation.

Most frequent causes of infertility in men

In men, infertility is associated with changes in sperm concentration and quality, ejaculation problems, varicocele, and exposure to harmful agents such as smoking and alcohol.

1. Ejaculatory problems

There are different types of ejaculatory problems that can be the origin of infertility.

These include premature ejaculation, due to systemic, psychological or inflammatory causes such as prostatitis. As well as the absence of ejaculation due to spinal cord problems that can be pharmacological (due to certain antihypertensives or antidepressants, among others), metabolic (diabetes) and psychological.

2. Varicocele

Infertility can be due to varicocele.
In addition to pain and testicular enlargement, a varicocele can cause infertility as a complication.

Varicocele is the dilation of the scrotal veins. It can cause testicular pain, the presence of a tumor in the testicle, or go unnoticed without symptoms. It is usually diagnosed when the couple is studied for infertility, as it affects sperm quality due to poor testicular development.

3. Sperm changes

Alterations in the concentration or quality of spermatozoa are associated with the use of tobacco or chronic alcohol consumption. This is also the case with urinary tract or genital infections, which in some way alter the quality of the sperm, decreasing its quantity and mobility. Similarly, sexually transmitted infections cause inflammation of the epididymis and accessory sex glands.

Infertility requires medical evaluation

These are just some of the most common causes of infertility, both in men and women. In the presence of difficulties conceiving a pregnancy or carrying it to term, a specialist doctor should be seen to determine the course of action to follow.

Genital infection is one of the most common causes of infertility, both in men and women, as it doesn’t only cause tubo-ovarian disorders, but it can also affect other parts of the anatomy of the reproductive system.

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