Causes of Female Sterility

From a medical perspective, sterility (the inability to fall pregnant) must be differentiated from infertility (the ability to fall pregnant but suffer repeated miscarriages). The investigation of the causes is based on clinical aspects. Below, we have listed possible causes of female sterility and how common they are.

Hormonal Causes

(Frequency approx. 30-40% of the purely female causes of sterility)

The harmonious functioning of the sensitive hormonal interaction between the diencephalon, pituitary gland and the ovaries is essential for a complication-free ovarian cycle. Under optimal conditions, a mature egg is produced in each cycle during the fertile phase of women between 15 and 40 years of age, and more irregularly beyond that age (up to 45 years). In principle, this egg is ready to be fertilised after ovulation. The hypothalamus acts as the superordinate component controlling the release of sex hormones such as FSH (follicle stimulating hormone), responsible for follicular maturation, and LH (luteinizing hormone), which triggers ovulation.

The perfect interplay between these hormones is influenced by other hormones, for example, prolactin, thyroid hormones, male hormones, and insulin. Variations occurring within this system can hinder correct follicular development.

External factors affecting this hormonal interaction, such as competitive sports, significant psychological stress, being over/underweight, drug,  nicotine and alcohol abuse can also cause sterility.

Hormonal disorders do not only have a negative effect on the ability to fall pregnant, but they can also cause miscarriage and have a negative influence on child development.

Tubal Sterility – Impairment of Fallopian Tube Function

(Frequency approx. 30-40%)

Adhesions or occlusions affecting the Fallopian tube can hinder the ability to fall pregnant. The causes of this problem can be wide-ranging. Fallopian tube occlusion is most common following inflammation, e.g., chlamydia, after surgery, or because of endometriosis or myomas.

Even in cases without complete occlusion, inflammation of the Fallopian mucous membrane can disrupt the transportation of the egg cell from the ovary to the uterus. Inflammatory processes (ovarian inflammation or appendicitis) often trigger local inflammatory reactions in the abdomen which promote the development of adhesions. These adhesions can limit the mobility of the Fallopian tubes and negatively affect their ability to take up the egg cell. During ovulation, the egg cell must be “caught” by the funnel-shaped end of the Fallopian tube to then be transported further down the tube, where fertilisation takes place. If there is a severe restriction affecting the passage of the egg cell or early-stage embryo, this can lead to a life-threatening condition known as a tubal or ectopic pregnancy.

Age

What many people do not realise or are not fully aware of is that one of the main causes of involuntary childlessness is advanced age, particularly of the woman!  The chance of a 30-year-old woman falling pregnant in a given month is 25%, for a 35-year-old woman it is 12-15%, and for a 40-year-old woman, it is only 1-4%. The reason for this is the decreasing number and quality of the egg cells, which increasingly often have genetic defects meaning they are less likely to result in a healthy pregnancy. This process begins at around 30 years of age and rapidly accelerates after 35 years of age. For the same reason, the rate of miscarriage increases with age. Even though women of 40 are nowadays not considered old, they should not wait too long to have children.

Uterine Sterility – Uterine Cavity-Related Causes

(Frequency approx. 5%)

There are various types of uterine malformations that can impair the implantation of the fertilised egg or have a negative effect on healthy embryonic development. Myomas (benign muscular growths) can also negatively affect fertility, depending on their size and location (uterine cavity, uterine wall, uterine surface). Endometrium polyps (local surplus mucous membrane production), starting at a size of approx. 10 mm, or adhesions resulting from inflammation or curettage, also known as scraping (also during abortions) can impair fertility.

A further problem is poor uterine mucous membrane development with no identifiable cause.

Recently, uterine miscolonisation with pathogens or underlying chronic inflammation of the uterine mucous membrane has been discussed as a cause of sterility. Maldistribution of lactobacilli also appears to play an important role.

Cervical Sterility – Cervix-Related Causes

(Frequency approx. 5%)

The cervix contains mucilaginous (gel-producing) cells which, during the ovulation phase, produce large amounts of mucus to aid the passage of the sperm into the uterine cavity. Previous operations (conisation), cervical tears or inflammation can impair the production of mucus and therefore represent a relevant factor in sterility. Oestrogen deficiency can also negatively affect the production of cervical mucus and stop the sperm from travelling from the vagina to the uterus.

Vaginal-Related Sterility

(Rare)

Malformations or stenoses can prevent intercourse. Inflammatory processes can promote miscarriage or premature birth.

Immunological Sterility

(Frequency unknown)

Although it can be assumed that various immunological factors play a role during the implantation phase, it remains completely unknown which immunological “deviations” require treatment and if they are even “treatable”. There continues to be a great deal of speculation about the significance of anti-sperm antibodies and possible rejection reactions between sperm and egg cell. Treatments based on the suspected immunological causes are controversial with doubt cast on their efficacy.

Blood Coagulation Disorders

(Frequency approx. 5%)

Various congenital coagulation disorders can negatively affect the probability of falling or staying pregnant without having any other obvious influence on daily life. These disorders are classed as thrombophilic disorders and, in some cases, can be successfully treated using coagulation inhibitors.

Chromosomal Disorders

(Frequency below 5%)

Congenital disorders, for example, numerical chromosomal aberrations (deviation from the normal number of chromosomes) in all or some cells of the body (mosaic formation), can also prevent pregnancy. Translocations can also increase the probability of the pregnancy being aborted (miscarriage).

Endometriosis and Sterility

Endometriosis is one of the most common causes of involuntary childlessness in young women. Over 50% of women who undergo a laparoscopy to determine the possible cause of their fertility-related problems are identified as having endometriosis.

How endometriosis develops has still not been definitively explained. Adhesions and Fallopian tube occlusions can result in “mechanical” obstacles. Endometrial cysts on the ovaries impair the maturation of the egg cell. These endometrial lesions lead to permanent inflammatory reactions in the abdominal cavity. It has been discussed that this can affect the maturation of the egg cell as well as the quality of the sperm and the implantation of the fertilised egg.

It is not always necessary to use IVF treatment. Your physician will provide you with detailed advice according to the stage of your illness. Spontaneous pregnancy is possible even with endometriosis. If endometriosis causes pain during sexual intercourse, then many couples have less intercourse or stop having sexual relations altogether.

More about endometriosis