Infertility: The Most Common Causes in Both Genders

Infertility is a sensitive issue that affects many couples and often comes with psychological stress. Approximately one in six couples in Germany has difficulty conceiving naturally. The causes of unwanted childlessness are varied and can lie with both women and men. Stress, lifestyle, and medical factors play significant roles.

In this article, we will explore the most common reasons for infertility in both genders. We will discuss risk factors, explain medical causes, and present diagnostic options. Additionally, we will inform about various treatment options, including assisted reproduction techniques.

Definition and Prevalence of Infertility

WHO Definition

The World Health Organization (WHO) defines infertility as the inability to conceive after more than twelve months of regular, unprotected sexual intercourse. This definition applies to both men and women. In professional language, the terms sterility and infertility are often used synonymously, although they originally have different meanings.

Sterility refers to the inability to achieve a pregnancy, while infertility describes the inability to carry a pregnancy to the birth of a healthy child. In the medical context, it is important to consider this distinction to enable precise diagnosis and treatment.

Infertility Statistics

Infertility is a widespread issue. According to a WHO study, about one in six people of reproductive age is temporarily infertile. Globally, 17.5 percent of all men and women are affected by the inability to conceive at some point in their lives.

In Switzerland, approximately one in five couples remains involuntarily childless. Worldwide, about one in six couples has difficulty conceiving and becoming pregnant within the first twelve months.

Primary vs. Secondary Sterility

There are two main forms of infertility: primary and secondary sterility.

• Primary Sterility: This occurs when a couple has never achieved a pregnancy. It is the inability to achieve a first pregnancy, either because the male sperm cannot unite with the female egg, or because the embryo cannot implant in the uterine lining.
• Secondary Sterility: This occurs when a couple has difficulty conceiving again after a previous pregnancy. This can also be the case if one partner has already had a child with another parent.

It is important to note that the causes of primary and secondary infertility can be different and due to various problems. Therefore, each case requires individual medical evaluation and treatment.

Risk Factors for Infertility

Age-Related Factors

Age plays a significant role in fertility, especially for women. Fertility declines slightly after the age of 30, markedly after 35, and significantly after 40. This is because eggs do not regenerate but age with the woman, decreasing in quality and increasing the likelihood of genetic abnormalities.

In men, the aging effect is less pronounced but still present. As men age, sperm quality can decrease, affecting the chances of successful conception.

Lifestyle Factors

Various lifestyle factors have a considerable impact on fertility:

• Smoking: It is proven to damage fertility in both genders. In women, it impairs ovarian function and hormone regulation; in men, it affects sperm production and quality.
• Weight: Both overweight and underweight can affect fertility. Overweight disrupts ovarian function and the hormonal system in both genders. Extreme underweight can lead to menstrual disorders in women.
• Exercise: Excessive exercise can be problematic. Extreme or competitive sports can put the body in a "flight mode," making reproduction more difficult.
• Stress: High stress levels can alter the menstrual cycle and affect the desire to have children.
• Alcohol and Drugs: Excessive alcohol consumption and drug use, such as cannabis, can disrupt hormonal balance and impair fertility.

Environmental Factors

Environmental factors play an increasingly important role in fertility problems:

• Endocrine Disruptors: These substances interfere with normal hormone functioning, including Bisphenol A (BPA) and phthalates found in canned goods or water bottles.
• Heavy Metals: Cadmium, lead, and mercury, found in industrial areas, can affect fertility.
• Pesticides: Studies show a link between pesticide exposure and declining sperm quality.
• Chemicals: Approximately 700 new chemicals are introduced to the North American market annually, with unknown effects on fertility.

These environmental factors can have long-term impacts on reproductive health, including disturbances in sperm production, ovarian function, and fetal development.

Medical Causes of Infertility

Common Causes in Women

Various medical factors can lead to infertility in women. A common cause is hormonal imbalance, which can prevent eggs from maturing properly, disrupt ovulation, or inadequately prepare the uterine lining for embryo implantation.

Thyroid dysfunction is particularly significant in young women, affecting the menstrual cycle, fertility, and fetal brain development during pregnancy.

Another hormonal disorder is hyperprolactinemia, characterized by elevated prolactin levels, leading to irregular cycles and impaired egg maturation.

Organic causes also play a role, such as blocked or damaged fallopian tubes due to inflammation, infections, or endometriosis, hindering egg transport.

Premature menopause occurs in about one in 100 women under 40 and one in 1,000 under 30, leading to early depletion of the egg reserve.

Common Causes in Men

The most common cause of infertility in men is the impaired production of normal, motile sperm. Reduced sperm quality can manifest in various forms:

• Oligozoospermia: Low sperm count in ejaculate.
• Asthenozoospermia: Reduced sperm motility.
• Teratozoospermia: High number of abnormally shaped sperm.

When all three issues are present simultaneously, it is called OAT syndrome (Oligo-Astheno-Teratozoospermia).

Factors affecting sperm production include:

• Undescended testes in childhood.
• Mumps or other infections.
• Varicoceles (varicose veins in the scrotum).
• Genetic anomalies such as Klinefelter syndrome.
• Environmental influences like heavy metals or pesticides.

Another common cause is the blockage of sperm pathways (obstructive azoospermia), where sufficient sperm are produced but do not reach the ejaculate due to blocked vas deferens or epididymis.

Idiopathic Sterility

In some cases, no clear cause for infertility can be found despite thorough diagnostics. This is known as idiopathic sterility. Estimates suggest that between 50% and 80% of couples with infertility, depending on the woman's age, struggle with this form of infertility.

In idiopathic sterility, minimal changes in both partners, which alone do not explain infertility, may combine to prevent pregnancy.

Despite the lack of precise diagnosis, affected couples can and should begin therapy. For women under 35, Clomifene citrate is often prescribed to stimulate ovulation, combined with intrauterine insemination. Good results can be achieved through in vitro fertilization with a good ovarian reserve.

It is important to note that the chances of natural pregnancy remain even with idiopathic sterility. About one-quarter of affected women conceive within a year without medical assistance.

Diagnosis and Treatment Options

Diagnostic Procedures

Infertility assessment begins with a thorough examination of both partners. For men, semen analysis is the most crucial test, evaluating sperm count, motility, and morphology. A normal semen analysis (normozoospermia) according to WHO criteria should meet specific parameters.

Further important tests for men include:

• Hormone analysis, especially testosterone and FSH.
• Ultrasound of the testes.
• Duplex sonography of testicular vessels.

For women, diagnosis starts with a detailed interview and physical examination, followed by:

• Ultrasound of the uterus, ovaries, and fallopian tubes.
• Endocrinological tests to check hormone production.
• Hysterosalpingo-contrast sonography (HSKS) to assess the uterus and fallopian tubes.
• Laparoscopy and hysteroscopy for suspected organic changes.

Conservative Therapies

Before considering invasive methods, conservative therapy approaches can be tried:

• Weight reduction in case of overweight.
• Lifestyle adjustments (e.g., reducing stress, alcohol, and nicotine).
• Hormonal stimulation of the female ovary.
• Treatment of underlying conditions like thyroid dysfunction or hyperprolactinemia.

For men, surgical treatment of a varicocele can be considered, especially if it is pronounced and has led to testicular shrinkage.

Assisted Reproductive Techniques

When conservative methods are unsuccessful, assisted reproductive techniques (ART) are used. The most common procedures include:

• Insemination: Inserting sperm into the uterus (intrauterine insemination, IUI).
• In-vitro Fertilization (IVF): Fertilization outside the body.
• Intracytoplasmic Sperm Injection (ICSI): Direct injection of a sperm into the egg.
• Cryocycles: Using frozen embryos.

In IVF, eggs are retrieved, fertilized outside the body, and then transferred to the uterus. ICSI is often used for male infertility and is similar to IVF, but a single sperm is directly injected into the egg.

It is important to note that these procedures can carry risks, such as multiple pregnancies or ovarian hyperstimulation syndrome. The success rate of infertility treatment averages between 10% and 20%, with just over 10% of parents taking a baby home.

Conclusion

Infertility poses a significant challenge for many couples, encompassing both physical and emotional aspects. The varied causes, ranging from hormonal disorders to environmental influences, necessitate thorough diagnosis. Modern medical procedures offer numerous ways to help affected individuals and improve their chances of conceiving.

Ultimately, it is crucial for couples with an unmet desire to have children to seek medical help early. The combination of lifestyle changes and advanced treatment methods can often lead to the desired success. Affected individuals should not lose hope, as there remains a possibility of natural pregnancy even with unexplained infertility.