Common causes of an unfulfilled wish to have a child
An unfulfilled wish to have a child affects many couples: Around one in six couples do not become pregnant naturally within a year. The causes are varied—and they may lie with the woman, the man, or both together.
Several factors often interact—and sometimes the initial examinations do not show any abnormal findings at first.
If pregnancy does not occur over a longer period, it can therefore make sense to clarify possible causes in a targeted way. It is not always necessary to wait for a specific period first: In cases of cycle disorders, known pre-existing conditions, or other indications of reduced fertility, earlier evaluation may also be advisable.
For sound diagnostics, it is crucial to involve both partners equally. Fertility disorders can have different causes—hormonal, functional, structural, or genetic. However, it is not always possible to identify a single cause—often a more complete picture only emerges from the interaction of various factors.
Below you will find an overview of the most common causes and possible influencing factors of infertility in women and men as a basis for targeted further diagnostics.
Common causes of fertility disorders
Hormonal disorders
Disorders of the female hormonal balance can mean that eggs do not mature, or only rarely mature, and ovulation does not occur. Signs may include irregular, very long, or absent cycles. More common hormonal causes include, for example, PCOS (formerly PCO syndrome, polycystic ovary syndrome), thyroid dysfunction, or an elevated prolactin level.
Thyroid dysfunction
Thyroid disorders affect the cycle, fertility, and early pregnancy. Both pronounced underactivity and overactivity can lead to cycle disorders and ovulation disorders, thereby impairing fertility. Common causes include, for example, Hashimoto’s thyroiditis or Graves’ disease. If you are trying to conceive, assessment of thyroid function is therefore part of the basic hormonal diagnostics.
Elevated prolactin level
Prolactin primarily regulates milk production after childbirth. If the level is elevated outside this phase, it can impair the hormonal control of the cycle and cause ovulation to occur less frequently or not at all. Possible causes include certain medications, an underactive thyroid, or—more rarely—a benign prolactinoma of the pituitary gland.
PCOS (formerly PCO syndrome, polycystic ovary syndrome)
Polycystic ovary syndrome is one of the most common hormonal causes of cycle and ovulation disorders. Typical features are irregular or absent ovulation and often elevated androgen levels. Possible accompanying symptoms include acne, increased body hair, or hair loss; some women also have insulin resistance. However, PCOS can vary greatly—not all features have to be present at the same time, and some women show only individual symptoms. Treatment is therefore tailored individually to the findings, the metabolic situation, and the wish to have a child.
Corpus luteum hormone deficiency (luteal phase deficiency)
After ovulation, the corpus luteum produces progesterone, which prepares the uterine lining for implantation and early pregnancy. A repeatedly shortened second half of the cycle can reduce the likelihood of pregnancy and should be examined more closely in cases of an unfulfilled wish to have a child. Spotting in the second half of the cycle can also be an indication of a cycle disorder. However, whether an isolated “corpus luteum hormone deficiency” represents an independent cause of infertility is not clearly proven scientifically. In addition, a single progesterone value is not sufficient to reliably assess the quality of the second half of the cycle.
Blocked fallopian tubes and reduced tubal function
Fertilisation takes place in the fallopian tube. If the fallopian tubes are blocked, damaged, or impaired in their function by adhesions, the egg and sperm cannot meet, or can only meet with difficulty. Common causes are previous inflammations, especially chlamydia infections, surgery, or endometriosis. Because changes in the fallopian tubes often do not cause symptoms, they frequently remain undetected for a long time.
Endometriosis
Endometriosis can impair fertility in different ways. Depending on severity and location, inflammatory changes in the pelvic area, adhesions, or endometriosis cysts can affect the function of the ovaries and fallopian tubes and change the conditions for fertilisation and implantation. The condition can vary greatly—from small superficial lesions to pronounced changes with adhesions or involvement of the ovaries. Not every case of endometriosis therefore inevitably leads to reduced fertility. Häufig wird sie erst im Rahmen einer Kinderwunschabklärung erkannt.
Changes in the uterus and uterine cavity
Changes in the uterus can impair the implantation of an embryo. These include fibroids and polyps as well as congenital changes in the shape of the uterus, for example a uterine septum. Whether a finding is relevant for fertility depends largely on its type, size, and location. In particular, changes that affect or distort the uterine cavity can influence the likelihood of pregnancy and may also be associated with an increased risk of miscarriage. Not every finding therefore needs to be treated—the decisive factor is an individual assessment.
Adenomyosis
The number of available eggs naturally decreases over the course of life. In some women, the ovarian reserve is already significantly reduced at a younger age. However, a low ovarian reserve does not mean that ovulation no longer occurs or that a natural pregnancy is ruled out. It can, however, be relevant in particular for planning fertility treatment. In premature ovarian insufficiency (POI), ovarian function is already significantly reduced before the age of 40. In this situation too, ovarian function can fluctuate and ovulation may still occur at times.
Reduced ovarian reserve and premature ovarian insufficiency (POI)
The number of available eggs naturally decreases over the course of life. In some women, the ovarian reserve is already significantly reduced at a younger age. However, a low ovarian reserve does not mean that ovulation no longer occurs or that a natural pregnancy is ruled out. It can, however, be relevant in particular for planning fertility treatment. In premature ovarian insufficiency (POI), ovarian function is already significantly reduced before the age of 40. In this situation too, ovarian function can fluctuate and ovulation may still occur at times.
Age and lifestyle
Age is a key influencing factor on female fertility. As age increases, not only does the number of available eggs decrease, but above all their quality. As a result, the likelihood of pregnancy decreases, while the risk of chromosomal abnormalities and miscarriages increases. In addition, factors such as smoking, excessive alcohol consumption, significant overweight or underweight can impair fertility.
Reduced sperm quality
The number, motility, and shape of sperm are among the most important parameters of a semen analysis. If too few sperm are present, their motility is reduced, or there are marked abnormalities in shape, the likelihood of natural fertilisation may decrease. Several parameters are often altered at the same time. However, an abnormal semen analysis does not automatically mean that a natural pregnancy is ruled out.
Increased DNA fragmentation and functional sperm disorders
Even with a normal semen analysis, there may be changes that are not captured by the classic assessment of sperm number, motility, and shape. This includes, for example, increased sperm DNA fragmentation, which may be associated with reduced fertility and less favourable pregnancy outcomes. In addition, functional disorders can impair a sperm cell’s ability to reach the egg, bind to it, or fertilise it. If there is a relevant clinical question, such changes are clarified with further examinations.
Varicocele (varicose vein in the testicle)
A varicocele is an enlargement of the veins in the area of the testicle. The increased temperature can impair sperm production. Whether surgical treatment is advisable depends on the extent of the impairment in the semen analysis and the individual situation.
Undescended testicle and diseases of the testicle
An undescended testicle (cryptorchidism) can impair later sperm production, especially if it is present on both sides or was treated late. Diseases or damage to the testicle, for example testicular tumours, inflammation of the testicle, or injuries, can also impair sperm production. In cases of testicular tumours, sperm quality may already be reduced before treatment begins.
Infections and inflammation
Infections and inflammation of the male genital tract can impair sperm quality and, in some cases, sperm transport. These include inflammation of the testicles or epididymis, for example after certain bacterial or sexually transmitted infections. Mumps orchitis, especially after puberty, can also permanently impair sperm production. Depending on the cause and severity, the changes may be temporary or permanent.
Impaired sperm transport
Even with normal sperm production, too few or no sperm may enter the ejaculate if the sperm ducts are blocked or not fully developed. Causes can include previous inflammation, surgery, or injuries, as well as congenital changes. In congenital absence of the vas deferens, for example, changes in the CFTR gene may be the underlying cause.
Genetic causes
Genetic changes are an important cause of severe male fertility disorders. These include Klinefelter syndrome with an additional X chromosome as well as so-called AZF deletions on the Y chromosome. They can impair sperm production to varying degrees—up to the complete absence of sperm in the ejaculate (azoospermia). In cases of marked abnormalities in the semen analysis, genetic evaluation is therefore often advisable.
Hormonal causes
Hormonal disorders can significantly impair sperm production. Sperm production is regulated by hormones from the brain, pituitary gland, and testicles. Conditions that disrupt this regulation can lead to reduced or absent sperm production. Depending on the findings, changes in FSH, LH, testosterone, or prolactin, for example, may play a role.
Medication, testosterone, and anabolic steroids
Certain medications can impair sperm production or sexual function. Particularly relevant are testosterone preparations and anabolic steroids: supplying testosterone from outside suppresses the body’s own hormonal regulation of the testicles. As a result, sperm production can decrease markedly or come to a complete stop. After discontinuation, sperm production often recovers, but this can take several months and is not always fully predictable. Other medications can also affect male fertility and should be taken into account in the medical history in cases of an unfulfilled wish to have a child.
Lifestyle and environmental factors
Lifestyle and external influences can also affect male fertility. Smoking, severe overweight, excessive alcohol consumption, and drug use can be associated with reduced sperm quality. Persistently high temperatures in the testicular area, for example due to frequent intensive heat exposure, can also temporarily impair sperm production. In addition, certain occupational or environmental exposure to harmful substances may play a role. How strongly individual factors affect fertility varies from person to person.
Age
In principle, men can remain fertile into older age. However, with increasing age, sperm quality and sperm DNA integrity can change, which may reduce the likelihood of pregnancy. At the same time, the risk of newly occurring genetic changes in sperm increases. Overall, the influence of age on fertility is less pronounced in men than in women.
After chemotherapy or radiotherapy
After radiotherapy or chemotherapy as part of cancer treatment, sperm production may be impaired temporarily or permanently. How strong the effects are depends, among other things, on the type and intensity of the treatment.
Erectile and ejaculatory disorders
Erectile and ejaculatory disorders are not uncommon even when trying to conceive and can make natural conception more difficult. This includes difficulties getting or maintaining an erection, as well as absent or impaired ejaculation. The causes may be physical, medication-related, or psychological; increasing pressure due to timed intercourse can also play a role. Early and open evaluation is advisable, as good treatment options can often be found.
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Targeted diagnostics
We examine possible causes step by step and involve both partners in the evaluation. Which examinations are appropriate depends on your individual situation and the findings already available.
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Clear medical assessment
You receive an understandable medical assessment rather than isolated findings. We explain what is relevant and which steps make sense.
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Personal medical support
A dedicated physician will accompany you through the evaluation, knows your medical history, and brings the individual results together into an overall picture.
Frequently asked questions about the causes of infertility
What are the most common causes of infertility in women?
Common causes include disorders of egg maturation or ovulation, endometriosis, changes in the fallopian tubes or uterus, and age-related changes in egg quality. Hormonal conditions such as PCOS, thyroid dysfunction, or an elevated prolactin level can also affect fertility. It is not uncommon for several factors to occur together.
What are the most common causes of infertility in men?
In men, changes in sperm production and sperm quality are the main focus. In addition, for example, varicoceles, diseases of the testicles, genetic changes, infections, disorders of sperm transport, as well as certain medications or testosterone preparations may play a role. Functional changes in sperm are also not always captured by a classic semen analysis.
How can reduced fertility be recognised in women?
Reduced fertility does not always cause symptoms. Irregular or absent cycles, very short cycles, or pronounced symptoms, for example with endometriosis, can provide indications. However, the cycle is often regular and the fertility disorder only becomes apparent because pregnancy does not occur over a longer period.
How can reduced fertility be recognised in men?
In men too, there are often no clear symptoms. As a rule, reduced fertility is only identified through a semen analysis, which examines the number, motility, and shape of sperm. Depending on the clinical question, further examinations may be advisable, as not all aspects of sperm function are captured by a classic semen analysis.
Can both partners have causes at the same time?
Yes. It is not uncommon for both partners to have factors that influence the likelihood of pregnancy. That is why, in cases of an unfulfilled wish to have a child, it makes sense to consider the woman and the man together from the outset and assess the findings in context.
Can the cause remain unclear even though all examinations are normal?
Yes. In some couples, the established examinations initially do not identify a clear cause for the unfulfilled wish to have a child. This is referred to as unexplained or idiopathic infertility. This does not mean that there is no cause, but that no clear explanation can initially be found with the available examination methods.
What role does age play in fertility?
Age is a key influencing factor on fertility, especially in women. As age increases, the number and, above all, the quality of eggs decreases. As a result, the likelihood of pregnancy decreases and the risk of chromosomal abnormalities and miscarriages increases. In men, sperm parameters and DNA integrity also change with increasing age, but the age effect is overall less pronounced.
When should I have it checked why pregnancy is not occurring?
As a guide, evaluation is recommended for women under 35 if pregnancy has not occurred after twelve months of regular unprotected intercourse. From the age of 35, evaluation should already take place after six months; for women over 40, immediate evaluation may be advisable. Regardless of age, earlier assessment is recommended if, for example, cycle disorders, endometriosis, known changes in the uterus or fallopian tubes, a possible reduced ovarian reserve, or indications of reduced male fertility are present.
Can lifestyle affect fertility?
Yes, factors such as smoking, alcohol, significant overweight or underweight, and environmental factors can impair fertility in women and men. Not every factor affects every person in the same way, but lifestyle factors play an important role.
Can I still become pregnant naturally despite reduced fertility?
Yes. Reduced fertility does not automatically mean that a natural pregnancy is ruled out. Many findings—for example reduced ovarian reserve, endometriosis, or an abnormal semen analysis—can reduce the likelihood of pregnancy without making it impossible. How high the individual chance is and how long it seems reasonable to wait further depends, among other things, on age, the cause and severity of the limitation, and the duration of the wish to have a child so far.
