What Are the Causes of Infertility in Males & Females?

By BSc, MSc (embryologist), MD, PhD (gynecologist), BSc, MSc (embryologist), BSc, MSc (embryologist) and BA, MA (fertility counselor).
Last Update: 10/24/2018

To find out the cause of infertility in a couple, a series of tests must be carried out on both the man and the woman. Depending on the results obtained in this fertility study, it will be possible to know whether the fertility problem is male, female or a combination of both.

Some of the most common causes of infertility are advanced maternal age, tubal lesions, alterations in sperm production and problems in the semen, endometriosis, etc.

Therefore, if after a year of regular sexual intercourse a pregnancy has not been achieved, it is recommended to visit a specialist to determine the origin of the problem in order to conceive.

Below you have an index with the 9 points we are going to deal with in this article.

Main causes of infertility in couples

Infertility issues in couples can be caused by the man, the woman, or both. Statistics show a similar frequency, with 30% of the cases having a male origin, and another 30% a female one.

The remaining 40% can be distributed between mixed or combined causes, which occurs in 20% of the cases, and unexplained infertility, present in another 20%.

In the case of mixed-cause infertility, both partners have alterations in their fertility that are causing their inability to have a child. On the other hand, in cases of infertility of unknown origin, no explanation for the problem can be found.

Female infertility

When it comes to female infertility, the causes may be varied but interrelated, and may be caused by different factors. Thus, a woman can have any of the following dysfunctions:

Ovary problems
Due to either problems with ovulating, or poor egg quality.
Tubal factor
Due to Fallopian tube problems, which can prevent or hinder the passage of the oocyte and the sperm.
Cervical factor
Problems with the cervix, which can hinder or even block the pathway of sperm toward the egg.
Uterine factor
Uterine fibroids, uterine adhesions, uterine abnormalities, poor endometrial development...

You may also enjoy some further information reading this: What Causes Female Infertility? – Definition, Signs & Treatment.

Ovarian causes

Hormonal alterations in the menstrual cycle of the woman can prevent ovulation (i.e. anovulation), cause it to occur in the wrong moment, or occurs but the eggs are produced incorrectly.

The endocrine system is responsible for controlling the ovarian cycle. For this reason, alterations caused by stress, obesity, low weight, thyroid gland problems, medications, etc. can affect the normal functioning of the ovary.

To examine the ovary and ovulation, the specialist runs a series of ultrasounds and hormonal blood tests to look for potential pathologies that may be causing infertility in the patient.

We recommend you visit the following link for more in-depth information: What Are the Endocrine Causes of Female Infertility?

Tubal causes

By tubal factor infertility we refer to any abnormality or dysfunction that appears in the Fallopian tubes of females. This organ allows two major events:

  • The egg-sperm binding.
  • The journey of the embryo to the uterus.

Thus, if the tubes do not carry out their function, the woman will be infertile. This happens when block tubes are blocked due to a variety of reasons, such as salpingitis, malformations, hydrosalpinx, endometriosis, etc.

In order for a diagnosis of tubal problems to be rendered, performing a hysterosalpingography (HSG) is necessary. This is an essential test when it comes to evaluating female fertility. As long as tubal patency exists in one tube, that is, as long as one tube is not blocked, pregnancy can take place.

You have much more information on this topic in the following article: Tubal Factor Infertility - Causes & Treatment.

Cervical causes

If sperm cannot go through the cervix, they will never reach the egg. Abnormal growths in this part of the female reproductive system, including polyps or fibroids, along with abnormalities of the cervical mucus can lead to infertility in the woman.

When the specialist suspects that this may be the reason for the fertility problem, he or she will order tests such as a postcoital test, microbiological cultures or a hysteroscopy, for example.

If you are interested in this reason for female infertility, we advise you to continue reading the following article: Female infertility owing to a cervical factor.

Uterine causes

Uterine abnormalities, including malformations or endometrial problems, can cause infertility issues by preventing implantation or a full-term pregnancy.

Amongst the most common uterine causes of infertility, we can mention endometriosis, fibroids, and polyps. Read more: Uterine Factor Infertility – Diagnosis, Characteristics & Treatment.

Male infertility

As regards male infertility, there exist four types depending on the cause:

Pre-testicular factor
Due to hormonal imbalances, the testes are not fully developed or are unable to carry out their function.
Testicular factor
Testicular disorders, whether congenital (from birth) or acquired.
Post-testicular factor
Including abnormalities of the seminal ducts, sexual impotence, or any kind of urinary tract infection.
Sperm disorders
All types of alterations in sperm parameters.

Click here to read more: What Causes Male Infertility? – Symptoms, Treatment & Statistics.

Pre-testicular causes

It includes hormonal causes due to a poor endocrine regulation. As a result, the development of any of these parts can be altered:

  • Testicles
  • Seminiferous tubules
  • Spermatogenesis (sperm production process)
  • Male reproductive system in general

A blood test for hormone levels is the only test that can detect pre-testicular causes of male infertility.

Testicular causes

It refers to any kind of disorder or defect in the testes, whether congenital or acquired.

Congenital defects
Usually due to genetic abnormalities, like the Klinefelter syndrome.
Acquired defects
They can be caused by medications, drugs, infections, trauma, or conditions, like varicocele or orchitis.

You can read more in depth at this link: Testicular Disorders & Infertility - Impact on Reproductive Function.

Post-testicular causes

This type of infertility is due to abnormalities or disorders in the seminal ducts, which include the epididymis, vasa deferentia, and urethra. Sperm must go through this pathway before being released with ejaculation.

In this case, infertility can be due to infections, blockages, or trauma. All of them can prevent sperm from being ejaculated.

Sperm disorders

The leading cause of male infertility. It is due to disorders in the sperm, whether they affect their morphology, vitality, or count.

The following are the most common sperm disorders:

Oligospermia or oligozoospermia
Low sperm count.
Poor sperm motility.
Teratospermia or teratozoospermia
High amount of abnormally shaped sperm.
Necrospermia or necrozoospermia
Elevated presence of dead sperm.
Zero sperm count.

The only method to detect the presence of a sperm disorder is a semen analysis, also known as seminogram or sperm test.

Mixed causes of infertility

In some cases, childlessness is present in both partners. In other words, the cause(s) of infertility will be the result of combining any of the male and female infertility issues mentioned above.

Nonetheless, in some cases infertility is due to immunological incompatibility. In these cases, the immune system of the woman attacks the sperms of the man. For this reason, both members may be fertile and are examined individually, but together conception is not possible unless they seek medical assistance.

According to Dr. Gorka Barrenetxea, Obstetrician & Gynecologist specialized in Reproductive Medicine:

It is common for us to find abnormalities in both members of the couple, including a sperm count under the normal reference values, a diminished ovarian reserve, tubal problems, etc.

Unexplained infertility

When the cause of infertility is unclear, we refer to it with the term unexplained infertility or unknown infertility. It occurs in approximately 20% of the cases. Despite performing the appropriate tests, specialists fail to find a cause that explains why the woman is not getting pregnant.

Unexplained infertility does not translate into the absence of fertility issues, but into unavailability of specific tests that allow the detection of whatever is causing infertility in the couple. Some cases are so challenging that the different tests available nowadays are insufficient to find the actual cause of sterility.

The good news is that unknown infertility can be tackled with Assisted Reproductive Technology (ART) as well, namely Intrauterine Insemination (IUI) or In Vitro Fertilization (IVF).

You can find much more information on this topic here: What Is Unexplained Infertility? - Causes, Diagnosis & Treatment.

Considering undergoing a fertility treatment? By getting your individual Fertility Report your will see different clinics especially selected for you out of the pool of clinics that meet our strict quality criteria. Moreover, it will offer you a comparison between the fees and conditions each clinic offers in order for you to make a well informed choice.

FAQs from users

Can low sperm volume cause infertility?

By Zaira Salvador BSc, MSc (embryologist).

Only if it comes along with other sperm abnormalities, such as low sperm count, poor sperm motility, and/or abnormal sperm morphology. When it is only a case of hypospermia, these males are still able to achieve pregnancy, either naturally or by means of ART.

Can HPV cause infertility in males?

By Zaira Salvador BSc, MSc (embryologist).

Some studies link the infection of semen with HPV to an impairment of sperm parameters, which suggests a potential role in male infertility, particularly in sperm motility. Also, it has been related to an increased risks of miscarriage among couples undergoing IVF, especially when HPV DNA was found in the semen sample of the male partner.

Can Chlamydia cause infertility in males?

By Zaira Salvador BSc, MSc (embryologist).

Yes, recent studies have shown that Chlamydia can harm the quality of the male sperm, as the degree of sperm fragmentation in these men's sample is almost three times higher than in healthy males. Poor sperm motility, having defective shapes, or a low sperm count are the sperm parameters that could be affected by a Chlamydia infection.

Do cats or dogs cause infertility in humans?

By Andrea Rodrigo BSc, MSc (embryologist).

To date, there is no evidence of a link between common pets and infertility. Having dogs, cats, hamsters or others will not affect your fertility. However, there exist certain parasitic infections that can be passed from them to humans and might have a negative impact on human fertility. As for cat allergy, there exist no studies that show a link between it and human infertility either.

On the other hand, people who work with livestock could be infected with certain diseases such as brucellosis, which symptoms include fever, chills, aches, sweating... In short, it might cause the body not to work optimally, and therefore affect a couple's reproductive efforts.

Can birth control cause female infertility?

By Sara Salgado BSc, MSc (embryologist).

Women who have been using hormonal contraception for a long period of time can take several month to recover normal menstrual cycles, and therefore their fertility. So the answer is yes, hormonal contraceptives can cause temporary infertility in females.

What are the causes of infertility at age 40?

By Sara Salgado BSc, MSc (embryologist).

In couples where the woman is 40 or older, it is likely that the cause of infertility is due to ovary problems associated with advanced maternal age. It is quite common for women at this stage in their reproductive years to experience hormonal imbalances that cause their menstrual cycle to develop inadequately. Moreover, the ovarian reserve experiences a dramatical decrease from age 35 onwards.

Does autoimmune thyroiditis cause infertility?

By Zaira Salvador BSc, MSc (embryologist).

Yes, autoimmune thyroiditis, also known as Hashimoto's disease, is the most common cause of hypothyroidism. The woman's body makes antibodies that attack the thyroid gland. As a result, a decrease in the amount of thyroid hormones occurs, causing irregularities in the menstrual cycle, among others.

You may also enjoy some further information reading this: Impact of Thyroid Hormones on Female Fertility.

Can stress cause female infertility?

By Zaira Salvador BSc, MSc (embryologist).

Yes. As a matter of fact, in todays modern, fast-paced society, it is a common cause leading to female and male infertility. In the case of women, the presence of a adrenalin can signal to the body that it is not the right time for conception, thereby preventing pregnancy.

Adrenalin also causes the pituitary gland to produce prolactin. This can cause infertility by inhibiting the releasing of GnRH, a hormone responsible for the production of sex hormones, may suppress ovulation.

Can Chlamydia cause infertility forever?

By Zaira Salvador BSc, MSc (embryologist).

If untreated, Chlamydia can affect a woman's fertility in many ways. If the infection spreads from the vaginal canal into the uterus, it can cause pelvic inflammatory disease (PID) and the endometrium to swell and scar. In most severe situations, this scar tissue can prevent implantation or cause an ectopic pregnancy.

Can drinking cause infertility?

By Zaira Salvador BSc, MSc (embryologist).

Yes, it can. According to some doctors, it lowers testosterone levels in mens, and decreases the quality and the quantity of sperm. In fact, it some cases, it can affect libido in males and females, as well as cause impotence in men.

Can HPV cause infertility in females?

By Zaira Salvador BSc, MSc (embryologist).

The human papillomavirus (HPV) alone should not have a huge impact on fertility. Although some studies have found that IVF patients who screened positive for HPV were less likely to have a baby, the reasons behind this affirmation are still unclear.

Some investigations have found that it is because an embryo might find it harder to implant in a woman whose immune system is unable to clear the virus. However, the vast majority are able to get pregnant without problems.

Can uterus didelphys cause infertility?

By Zaira Salvador BSc, MSc (embryologist).

Uterus didelphys rarely causes problems. In fact, some women don't even know they have it, while others experience very painful menstrual periods. Uterus didelphys can be the cause of recurrent miscarriages. Though rarely, if the woman gets pregnant with fraternal twins, they might be delivered hours or days apart.

Does mumps cause infertility in males?

By Zaira Salvador BSc, MSc (embryologist).

Childhood diseases such as mumps or chicken pox normally run their course and end without significant long-term effects. However, when a boy or an adult man contracts mumps, it can affect the testes and cause a condition called orchitis.

The prevalence of orchitis in young adults and adults ranges from 20% to 30%. Only in a small percentage of mumps-induced orchitis, the male experiences a reduction in sperm production, probably linked to changes in male hormones during the earliest stages of orchitis.

Can a sedentary lifestyle cause infertility?

By Zaira Salvador BSc, MSc (embryologist).

A sedentary lifestyle is not beneficial in any way, especially for women than men. Several studies suggest that a sedentary lifestyle as a teenager can cause hormonal imbalances and anovulatory cycles, consequences more commonly seen in PCOS patients. In the case of men, those with a sedentary lifestyle tend to be overweight or even obese, which leads to low sperm quality. So, in short, to prevent infertility you should stay active and eat right.

Suggested for you

If you have just received a diagnosis of infertility and been referred to fertility treatment, you might feel a bit overwhelmed due to so much new information. You can learn more here: What is Assisted Reproductive Technology (ART)? – Techniques & Costs.

Throughout this post, what you found is a brief summary of the different causes of male and female infertility. If you wish to delve deeper into the tests performed to identify them, we recommend that you visit any of these posts:

Finally, one of the most concerning aspects for patients who are going to start a fertility treatment is whether it will actually work for them. You can clarify your doubts here: Success Rates in Assisted Reproduction.

Our editors have made great efforts to create this content for you. By sharing this post, you are helping us to keep ourselves motivated to work even harder.


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FAQs from users: 'Can low sperm volume cause infertility?', 'Can HPV cause infertility in males?', 'Can Chlamydia cause infertility in males?', 'Do cats or dogs cause infertility in humans?', 'Can birth control cause female infertility?', 'What are the causes of infertility at age 40?', 'Does autoimmune thyroiditis cause infertility?', 'Can stress cause female infertility?', 'Can Chlamydia cause infertility forever?', 'Can drinking cause infertility?', 'Can HPV cause infertility in females?', 'Can uterus didelphys cause infertility?', 'Does mumps cause infertility in males?' and 'Can a sedentary lifestyle cause infertility?'.

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Authors and contributors

 Andrea Rodrigo
Andrea Rodrigo
BSc, MSc
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics. More information about Andrea Rodrigo
 Gorka Barrenetxea Ziarrusta
Gorka Barrenetxea Ziarrusta
Bachelor's Degree in Medicine & Surgery from the University of Navarra, with specialty in Obstetrics and Gynecology from the University of the Basque Country. He has over 30 years of experience in the field and works as a Titular Professor at the University of the Basque Country and the Master's Degree in Human Reproduction of the Complutense University of Madrid. Vice-president of the SEF. More information about Gorka Barrenetxea Ziarrusta
License: 484806591
 Sara Salgado
Sara Salgado
BSc, MSc
Degree in Biochemistry and Molecular Biology from the University of the Basque Country (UPV/EHU). Master's Degree in Human Assisted Reproduction from the Complutense University of Madrid (UCM). Certificate of University Expert in Genetic Diagnosis Techniques from the University of Valencia (UV). More information about Sara Salgado
 Zaira Salvador
Zaira Salvador
BSc, MSc
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Sandra Fernández
Sandra Fernández
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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