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Causes of infertility

  1. Male infertility
  1. Ovulation problem
  2. Tubal problems
  3. Uterine problems
  4. Cervical Mucus Hostility
  1. Immunological infertility
  2. Coital failure
  3. Unexplained infertility

The different causes of infertility

The goals of evaluating infertile couples are to determine the cause of infertility and hence make recommendations about the treatments available and evaluate the chances that such treatments will help. In approximately 30% of infertile couples, the cause is identified only in the female and in 30% the cause is identified only in the male. In 30% of couples, causes can be detected in both partners. In about 10% of cases, the underlying cause is not yet found by the current diagnostic methods.

Determining the causes of infertility.

Go to the investigations page if you want to know more about the ways in which the causes of infertility can be determined.

Alternatively, find out about the treatment options for a particular cause of infertility.


Male infertility

Male infertility is defined as the inability of a man to father a child. Although male infertility may be associated with impotence, many infertile men have perfectly normal and happy sexual relationships.

Male infertility can be classified into four main types:

  • No sperm (azoospermia) accounts for 3-4% of male infertility.
  • Poor sperm quantity (oligospermia) or quality e.g. low motility (asthenozoospermia) or a high percentage of abnormal sperm (teratozoospermia). Antisperm antibodies, etc. This subgroup may account for about 90% of male infertility.
  • Sperm dysfunctional, where there is a normal semen analysis but the sperm lack or have a defective fertilizing capacity, resulting in complete failure of fertilization or poor fertilization of the eggs in IVF. This accounts for 3-6% of male infertility.
  • Inability to ejaculate into the vagina. This accounts for 4-6% of male infertility.

In the majority of men suffering male infertility, physical and genital examinations reveal no cause of infertility, but in a few cases, it may reveal abnormalities such as poor facial and bodily hair, enlarged breasts, undescended testis, small testes or varicocele.




Male infertility due to no sperm in the ejaculate.

Possible causes include either failure of the testicles to make sperm, or the testicles are making sperm but because the vas deference are either blocked or congenitally did not develop, no sperm is seen in the ejaculate. In the majority of men in whom the testicles are not making sperm, there is no apparent reason. However, in a few there is history of trauma to the testicles, severe mumps infection after puberty, or the pituitary gland is not producing enough hormones. Chemotherapy or radiotherapy for cancer might have damaged the testicles.

Semen freezing should be made available to men undergoing medical treatment that is likely to make them infertile as effectiveness of semen freezing is well established.

Genetic defects e.g. chromosomal abnormality such as Klinefelter's syndrome, and Y chromosome deletion (a tiny abnormality in the area of a Y chromosome which affects fertility) may also lead to no sperm in the ejaculate.

Some cases of congenital bilateral absent of vas (the tube that carries the sperm) are associated with cystic fibrosis. In some infertile men, the absence of sperm in their ejaculate is due to retro-grade ejaculation (during orgasm, sperm enter the bladder and mix with urine, rather than are ejaculated into the vagina). This is a rare condition and accounts for less than 1% of male infertility, retrograde ejaculation may follow surgeries such as the removal of prostate and can be a side effect of certain drugs etc. As the sperm are normal, they may be recovered from the urine and used for insemination or IVF.

Male infertility due to poor sperm quantity or quality

This could be due to many factors such as hormone deficiency, varicocele (abnormal swollen blood vessels around the testicles), infection, drugs such as antidepressants, antihypertensive drugs (taken for high blood pressure), anabolic steroids used for body building and social drugs such as marijuana and cocaine, heavy smoking and excess alcohol. Other causes include frequent hot baths and saunas. Testicular cancer is also associated with an increased risk of impaired sperm production (it occurs in middle age men, whereby the risk is increased in men who have had a history of undescended testicles). Furthermore, antibodies to sperm (antisperm antibodies) adversely affect sperm production.

Male infertility due to impaired sperm fertilizing capacity

This could be due to defective acrosomes, abnormal lateral head movements of sperm, inability of sperm to bind to the zona pellucida, or excess free oxygen radicals in the semen.

Male infertility due to the inability to ejaculate into the vagina

This could be due to impotency, premature ejaculation, or the inability to ejaculate.


Ovulation problems

This is the commonest cause of female infertility and it is also the one with the best chance of successful treatment. The woman usually presents with infrequent or very scanty periods, irregular periods or absent periods altogether (amenorrhoea). However, ovulation dysfunction can occur with apparently regular cycles. Sometimes women may notice an increase in body and facial hair, acne, milk secretion from her breasts etc.

Ovulation disorders can be classified into:

  • Annovulation i.e. lack of ovulation
  • Oligoovulation i.e. infrequent ovulation
  • Luteal phase defects





Here, the problem is in the ovary itself e.g.

  • The ovaries were surgically removed.
  • The ovaries were damaged by radiotherapy or chemotherapy treatment for cancer.
  • The ovaries only have a few eggs in them i.e. premature menopause which affects 1-2% of women below the age 40 years.
  • The woman was born without ovaries.
  • Some women have polycystic ovaries.


Here, the ovaries are not the problem, but the lack of hormones released from the pituitary gland or hypothalamus. Causes include the following:

  • Severe stress.
  • Recent great gain or loss of weight.
  • Certain drugs.
  • Tumor (growth).
  • Excess production of  the hormone prolactin.
  • Disturbances involving the thyroid gland and the adrenal glands.

Luteal phase defect

This is defined as either a defect of progesterone secretion by the corpus luteum or a defect in the lining of the womb response to hormonal stimulation. This results in an inadequate lining of the womb for embryo implantation. It is estimated that luteal phase defects affects 3-20% of infertile couples.


Tubal problems

Tubal damage is a common cause of infertility. Damage to the fimbriae may reduce or stop their ability to pick up the egg and direct it into the Fallopian tube. Adhesions around the tube may distort the tube or reduce their mobility, thus affecting their ability to pick up the egg. Damage to the cells lining the tube may prevent sperm from reaching the egg or greatly reduce the chance of fertilization. Blockage of the tube can prevent the sperm from reaching the egg, or the fertilized egg from moving to the uterus and increases the incidence of ectopic pregnancy. Tubal blockage can be either proximal or distal. The former is where the blockage is located close to the uterus, while the latter is where it lies at the fimbriae.

Most women will not be aware of the tubal damage until they have been investigated for infertility. However, some may have severe period pains, irregular or heavy periods, chronic or recurrent pelvic pain and tenderness.





This is the commonest cause of tubal damage. Especially if the infection goes untreated or is treated inadequately at the time e.g.

  • Previous pelvic infection.
  • Sexually transmitted diseases such as chlamydia and gonorrhoea.
  • Wearing a coil (IUCD) can lead to infection in the womb, which can spread to the tubes.
  • Spread of infection from internal organs such as appendicitis, bowel infection.
  • After an abortion, miscarriage or delivery, an infection may spread to the tubes.


Any surgery that involves the Fallopian tubes, ovaries and uterus can cause adhesions. Sometimes abdominal surgery can also result in adhesions that may affect the tube.

Previous ectopic pregnancy

Previous ectopic pregnancies can be a cause of tubal damage.

Congenital abnormality

This is an abnormal development before birth such as an absent or maldeveloped tube.


The condition endometriosis can lead to scarring of the tubes, adhesions, and in severe cases to blockage of the tubes.


Hydrosalpinx is a blocked, dilated, fluid filled Fallopian tube usually caused by a previous pelvic infection. In mild cases fertility may be restored by opening the tube surgically, otherwise IVF is the treatment of choice. There is some evidence that hydrosalpinx reduces the success rate of IVF and increases the risk of mscarriage. For this reason, some doctors may advise removing, or occluding the hydrosalpinx before the IVF treatment.


Uterine problems

Many women who have uterine problems may have no problems getting pregnant, but they may have difficulty in keeping the pregnancy as they tend to miscarry. Most women have no symptoms, some women will have scanty periods, and if the woman has no uterus she will have no periods, (but remember there are many causes of absent periods). Some patients may also complain of heavy periods (due to fibroids).





Fibroids are benign growths of the muscle of the womb; they are very common especially in older women. Many women who have fibroids are fertile and have no problems with keeping the pregnancy. However, if the fibroid significantly distorts the cavity of the womb, it may interfere with embryo implantation. Also fibroids can displace the Fallopian tubes and ovaries.

Multiple uterine fibroids

Uterine Polyps

Uterine polyps, these are very common small growths dangling in the cavity of the womb. They can interfere with conception by acting like a coil.

Hysteroscopic view of an endometrial polyp.

Adhesions in the uterine cavity (cavity of the womb) may be a consequence of infection or surgery such as D&C (scraping of the uterus).

Congenital Problems

Congenital problems (problems from birth) e.g. absent uterus, the uterus has not developed sufficiently in size (hypoplastic uterus). Abnormally shaped uterus such as double uterus, birconuate (two-horned uterus) and uterine septum.


Antibodies are substances that circulate in the blood and body tissues, and which normally protect the body from invasion by foreign bodies such as bacteria and viruses, in order to prevent the body from getting an infection. For unknown reasons the body may develop antibodies against sperm. The sperm will then be “sensed” as foreign and are attacked by the body in a similar fashion to the way that the body attacks infecting organisms.

Antisperm antibodies can be present in either or both partners. It can be present either in the blood or in the genital tract secretions such as cervical mucus and ejaculate. 

There are different types of antibodies e.g. IgG, IgA and IgM. Antisperm antibodies in the ejaculate will make the sperm ineffective by making them stick together and preventing them from being released. In the female, antisperm antibodies may interfere with the process of sperm transport and fertilization.




Unknown but there are associations with genital infection, trauma to the testicles, varicocele, vasectomy and after reversal of vasectomy.


Cervical Mucus Hostility

The cervical mucus is a jelly-like substance produced by minute glands in the cervical canal. It changes in consistency and composition with the menstrual cycle. Just before ovulation and under the effect of the hormone estrogen it becomes very watery and copious to allow the sperm to swim through it. After ovulation and under the effect of progesterone, the mucus becomes thick and sticky, which render it impenetrable to the sperm. Once the sperm are in the mucus, they can stay there for a few days. Thus the mucus acts as a sperm reservoir.

Cervical mucus hostility is the inability of sperm to penetrate the cervical mucus. The significance of cervical mucus hostility is disputable among infertility specialists. Problems with cervical mucus usually cause no symptoms.




  • The mucus is too sticky and thick (and there is not enough of it to allow sperm to swim through). This may be due to poor estrogen stimulation of the cervical glands (e.g. wrong timing of the test or lack of ovulation) or poor functioning cervical glands due to infection or damage caused by surgery, as may occur after cone biopsy.
  • Mucus contains antisperm antibodies.
  • Abnormal or defective sperm.

The term endometriosis refers to a benign and common disease in which cells like the ones that line the inside of the womb are established outside the womb e.g. on the ligament supporting the uterus. in the ovaries, tubes, pelvis, bowels, bladder, etc. In patients with endometriosis, these cells, like the endometrium, respond to the monthly hormonal changes. When the woman with endometriosis menstruates, the endometrium is shed in the form of a period, the endometriosis breaks down in the same way but because these cells are trapped inside, and cannot escape, they form swellings filled with dark blood (known as chocolate cysts) and adhesions which may damage the tubes.

Endometriosis seen through endoscope.

Endometriosis tends to occur in women who are in their 30s and early 40s, but occasionally occurs in those under 30 years of age.

Some patients with endometriosis may have no symptoms; some may experience considerable pain during their periods or during intercourse and their periods tend to be heavy.

On vaginal examination their may be tenderness and thickening of the supporting ligaments of the uterus in women with endometriosis. Ovarian cysts may also be felt by the doctor.

The majority of women with endometriosis are fertile. However, some women may experience difficulty becoming pregnant.

How does endometriosis cause infertility?

The anatomical distortion caused by endometriosis, specially when it is moderate and severe, could explain a mechanical cause of infertility, the precise mechanism by which minimal and mild endometriosis affect fertility is not fully understood. It is possible that endometriosis adversely affect the egg development, sperm binding to the egg, fertilization, tubal function and embryo implantation.


The only means of diagnosis of endometriosis is by laparoscopy, which assesses the severity of endometriosis and the condition of the Fallopian tubes. There are a number of different classification systems for endometriosis, but the most widely used is that of the American Society for Reproductive medicine (ASRM) in which endometriosis is classified into four stages: minimal, mild, moderate and severe. There is little correlation between the severity of symptoms and extent of the endometriosis.

Ultrasound scans, CAT scans, or MRI scans, can identify cysts on the ovaries. However, these techniques can not be used to make a definitive diagnosis of endometriosis.




Cause is unknown. However, the most widely accepted explanation for endometriosis is that viable cells from the lining of the womb pass upwards into the Fallopian tube and out into the pelvic cavity where they settle down. In most women these cells will be destroyed by the woman's immune system. However, in some women, these cells implant and proliferate, possibly due to a disorder of the womans' immune system.


Coital failure

Some infertile couples may experience difficulty in having a baby because of coital difficulty or inappropriate timing of sexual intercourse (infrequent intercourse or intercourse mainly at the beginnings and the ends of the womans menstrual cycle). Coital difficulty may also result after a sexually active couple has been labeled infertile. For some couples, sexual intercourse becomes a necessity rather than a natural love making experience. Infertility investigations itself can be very stressful to the couple.

Many men and women suffer for years without seeking advice and help. This is often because they are unaware that in most cases, treatment may help. Some do not know whom to turn to for advice and others are too embarrassed to seek help.

The causes of the sexual difficulty could be physical or psychological. However, most cases will involve physical and psychological elements, although the balance may vary considerably from person to person.

Coital difficulty requires appropriate investigations and treatment. When the cause is predominantly psychological, normal sexual functions may be restored through psychosexual therapy. In many cases, nothing more than sex education of both partners is necessary. Some men are concerned about the size of their penis and their ability to father a child. The size of the penis is generally unimportant so long as penetration is achieved.

If the cause of coital failure is predominantly physical, normal sexual activities are unlikely to be restored without some form of medical or surgical treatment.




Psychological causes

  • Emotional and financial stress and anxiety from home or work
  • Marital disharmony
  • Worry about poor sexual performance, fear of failure, fear of pregnancy
  • Depression
  • Inadequate or absent sex education
  • Sexual problems in the partner
  • Psychological trauma such as sexual abuse, rape or traumatic childbirth.

Physical causes

  • Damage to the special nerves which cause erection. This could have been the result of an injury such as spinal cord injury, surgery such as prostatectomy and surgery in the bladder neck, or diseases such as multiple sclerosis.
  • Deficient blood flow to the penis e.g. blocked arteries.
  • Chronic illnesses such as kidney or liver failure.
  • Side effects of prescribed drugs e.g. certain drugs for lowering high blood pressure.
  • Diabetes (30 % of diabetics suffer from some form of sexual dysfunction).
  • Hormonal e.g. hyperprolactinemia or low testosterone levels.
  • Heavy smoking
  • Alcoholism and drug abuse
  • Congenital penile abnormalities
  • Painful scar (e.g. episiotomy)
  • Infection
  • Congenital abnormalities such as a rigid and tough hymen or unusually narrow entrance.
  • Endometriosis



The absence of sexual desire "libido". The psyche is the seat of libido.

Premature ejaculation

The man arrives at orgasm and ejaculates before he wishes to do so.


The inability to achieve orgasm by means of masturbation or coitus. Although, it is not necessary for the woman to have an orgasm for conception to take place, unfulfilled sexual activity may create marital tension and stress.

Delayed (retarded) ejaculation

The inability to achieve an orgasm, even though the erection is satisfactory. At times retarded ejaculation is selective (a man is able to achieve an orgasm by masturbation but not during coitus).

Erectile dysfunction (ED)

Commonly referred to as impotence, it is the inability of the man to obtain or maintain an erection satisfactory for the purpose of sexual intercourse.


The pain experienced by the woman during intercourse. Dyspareunia could be superficial when the woman experiences pain in her vulva or vagina during penetration. Deep dyspareunia occurs when the woman experiences pain deep in her pelvis in the organs that surround the top of the vagina.

Vaginismus (vaginal spasm)

The inability of the woman to relax her vaginal muscles, preventing penetration by the male. Vaginismus is the commonest cause of dyspareunia. It can affect women who have never been pregnant before as well as women who have been pregnant before.


Unexplained infertility

The term unexplained infertility is defined as failure to conceive after one year of unprotected intercourse. Despite thorough investigations no apparent cause for the infertility was found.

Unexplained infertility


10-15% of couples but the actual figure depends upon the extent of investigations undertaken.


None, even after thorough investigations of both partners. However, possible causes include:

  • Defective fimbriae, the fimbriae are unable to pick up the egg at ovulation.
  • Sperm lacking the fertilizing capacity.
  • Defective endometrium which does not allow the embryo to implant.
  • Luteinized unruptured  follicle syndrome when, the follicle fail to release the egg at ovulation and thus the egg  is trapped inside the corpus luteum.
  • Psychological