Causes of male and female sterility

Causes of sterility in men

Impaired testicular function

Reduced semen quality may affect all three primary factors of sperm quality (sperm count, motility and percentage of sperm with normal morphology). Testicular damage caused by infection (including mumps), testicular varicose veins (varicocele) or job-related pressure or temperature factors, as well as irradiation, are also associated with sterility. If improperly descended testicles (testicular maldescent) are treated too late, reduced sperm quality will often result.

Malformed or blocked seminal vesicles

Certain genetic disorders or inflammations may result in the non-formation or adhesion of seminal vesicles. A highly febrile mumps infection may also play an important role in this process.

Hormonal imbalances

In relatively rare cases, hormonal imbalances are to blame for reduced sperm production. A common example of self-inflicted hormonal shifting is an imbalance resulting from the use of anabolic steroids.

Immune factors

For example, the prolonged backing up of sperm either due to infection or after a vasectomy (surgical dissection of the vas deferens) will result in the formation of antibodies against the man’s own sperm, thus reducing their fertility.

Prior vasectomy

The surgical dissection of the vas deferens as a method of male contraception results in the absence of sperm in the ejaculate.

Neurological and psychological factors

Paraplegia or prior surgeries on tumours in the genital region may result in erectile or ejaculatory dysfunction (impaired semen discharge). In patients with what is known as retrograde ejaculation, semen is discharged but into the „wrong“ direction, i.e. into the bladder. Psychological disorders may also cause libido disorder (reduced sex drive), along with the associated erectile dysfunction and ejaculation problems, and thus prevent pregnancy.

Chromosomal disorders

In certain chromosomal disorders, sperm fails to mature in the testicles, as a result of which even a testicular biopsy (the sampling of tissue from the testicles) cannot detect and mature, fertile sperm.


There are developmental disorders of the penis in which the urethra (the urinary duct) does not open at the tip of the penis but rather on the shaft, as a result of which ejaculation (the discharge of sperm cells) will not necessarily result in semen reaching the cervix.


Causes of sterility in women

Endometriosis and sterility

Endometriosis is one of the most common causes of unwanted infertility in young women. Laparoscopies performed to investigate fertility problems in women detect endometriosis in over 50 % of cases.

It is currently not fully understood how endometriosis develops.

Agglutination, adhesions and occluded fallopian tubes may cause „mechanical“ obstructions. Endometriotic cysts in the ovaries may prevent the egg cells from maturing. Lesions from endometriosis result in a persistent inflammatory reaction in the abdominal cavity. This may prevent the egg cells from maturing properly as well as affecting sperm quality or even preventing inseminated egg cells from adhering to the uterine wall.

IVF treatment is not always the first option in these cases. Your doctor will provide you with extensive advice depending on the stage of your condition. Spontaneous pregnancies are even possible in women with endometriosis. If endometriosis is causing severe pain during sexual intercourse, many couples will refrain from intercourse or not even sleep together any more.

More about endometriosis

The causes of sterility in women can be broken down into the following categories:

Hormonal causes (incidence: approximately 30 % of all causes of sterility in women)

The proper operation of the sensory hormonal mechanism between the diencephalon (interbrain), pituitary gland and ovaries (known as the „hypothalamic-pituitary-ovarian axis“) is important so that the ovarian cycle can function smoothly. Under optimum conditions, this mechanism will result in the formation of a mature egg which will in principle be fertile after ovulation in each cycle during a woman’s fertile phase (between the ages of 15 and 40). This will continue at increasingly irregular intervals beyond this phase (up to 45 years). The hypothalamus (part of the diencephalon) is the major structure in the brain which acts in this process to regulate the release of gonadotropins (sex hormones) such as FSH (follicle-stimulating hormone) which stimulates follicle maturation (egg vesicle maturation) and LH (luteinising hormone), which ultimately triggers ovulation.

Other hormones, such as prolactin, thyroid hormones, male hormones and insulin affect the ability of these hormones to interact perfectly. The smallest abnormalities within this system can disrupt normal follicular development.

External factors impacting this hormonal mechanism, such as strenuous exercise and major psychological stress, may also cause sterility.

Hormonal imbalances are not only a potential barrier to pregnancy. They may also have a negative impact on child development or cause miscarriage.

Tubal sterility (incidence: approximately 30 %)

Inflammation of the mucous membrane of the fallopian tubes can prevent egg cells from migrating from the ovary to the uterus (womb). In extreme but not at all uncommon cases, one or both of the fallopian tubes may become completely blocked. These changes are often triggered by bacteria such as Chlamydia.

Inflammatory processes (inflammation of the ovaries or of the coecum) often result in local inflammatory reactions which in turn lead to the formation of adhesions. This could cause reduced fallopian tube motility, thus hindering the capturing function of the ends of the fallopian tubes (fimbriae). During ovulation, the egg cell has to be captured by the fimbriae so that it can then be carried along the fallopian tube to where fertilisation will ultimately take place. If the passage of the egg cell or early embryo is severely obstructed, this can result in the premature nidation (implantation) in the fallopian tube, which in turn results in a life-threatening condition (tubal pregnancy).

Especially endometriosis, which is discussed in greater detail elsewhere, can act as a non-bacterial source of inflammation resulting in this condition and other consequences.

Uterine sterility (incidence: approximately 5 %)

There are various types of malformation of the uterus, such as septate uterus, subseptate uterus and arcuate uterus, which may disrupt implantation, as well as preventing the normal development of an embryo. Myomas (benign tumours in the muscle) can also affect fertility, depending on their size and location (uterine cavity, wall or lining). So-called endometrial polyps (localised excessive mucous membrane production) or adhesions after inflammation or following a D&C (including terminations of pregnancy) reduce fertility.

Another problem is the poorly developping lining of the uterus that has no discernible cause.

Cervical sterility (incidence: approximately 5 %)

Tears or inflammation in the cervix block the access of sperm. In particular, the propertery of the cervical mucous during the woman’s fertile phase can be changed due to an oestrogen deficiency in such a way that the sperm is prevented from ascending from the vagina towards the uterus (womb).

Vaginal sterility (incidence: approximately 5 %)

Malformations or stenoses (narrowing) may prevent sexual intercourse. Inflammatory processes may make miscarriage or premature birth more likely.

Immunological sterility (incidence: approximately 5 %)

There is still much speculation about the significance of sperm antibodies and a possible „rejection reaction“ between semen and egg cell. There is some doubt and controversy regarding the effectiveness of treatments that have been developed to treat presumed immunological causes.

Abnormal blood clotting (incidence: approximately 5 %)

Various congenital disorders affecting what is known as the „coagulation cascade“ can negatively impact a woman’s chances of becoming of staying pregnant without having any noticeable effect on her daily life. These disorders, known collectively as „thrombophilia“, can in some cases be treated successfully with anticoagulants.

Chromosomal disorders (incidence: approximately 5 %)

Congenital disorders such as numerical chromosomal aberrations (deviations from the normal number of chromosomes) in all or in some of the body’s cells (mosaicism) can also prevent pregnancies. They can also increase the likelihood of miscarriage.

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