Infertility refers to a couple’s inability to achieve pregnancy after 12 months or more of regular, unprotected sexual intercourse. In today’s world, infertility is becoming more common, affecting millions of people. It’s important to understand the major causes of infertility in men and women because the right information can lead to early detection and treatment.

Understanding the differences in infertility causes between men and women can help couples take the right steps. This blog will take you through the major causes of infertility in men and women, beginning with male factor infertility, followed by female infertility problems, and concluding with advice on when to seek help.

What Is Infertility?

Infertility is a medical condition defined as the inability to achieve pregnancy after 12 months of regular, unprotected sexual intercourse. If the woman is over 35, the timeframe is reduced to 6 months.

There are two types of infertility:

• Primary infertility – when a couple has never been able to conceive.
• Secondary infertility – when they’ve had at least one successful pregnancy in the past.

Globally, it is estimated that 1 in 6 people are affected by infertility. Both male infertility and female infertility contribute to this number, often equally.

Major Causes of Infertility in Men

Understanding the major causes of infertility in men and women begins with male-related issues. In men, fertility largely depends on the quantity and quality of sperm. To identify the problem, doctors recommend semen analysis which is performed following the guidelines established by the World Health Organization (WHO) in its 6^th edition of the Laboratory Manual (2021).

This manual provides standardized, evidence-based procedures to ensure test results are consistent and comparable globally. For clinicians and patients, the key reference point is the set of lower reference limits (5th percentile values derived from fertile men), which serve as crucial indicators for assessing fertility potential.

The critical lower reference limits for basic semen parameters are:

• Semen Volume:4 mL
• Sperm Concentration: 16 million/mL
• Total Sperm Number: 39 million per ejaculate
• Progressive Motility (PR): 30%
• Total Motility (PR + non-Progressive): 42%
• Sperm Vitality (Live Spermatozoa): 54%
• Normal Morphology: 4%

These values are not strict “pass/fail” thresholds for fertility, but rather indicators used by specialists to assess the likelihood of male factor subfertility and determine the appropriate next steps in diagnosis and treatment.

• Low Sperm Count (Oligospermia)

This is when the semen contains fewer sperm than normal. A low sperm count makes it harder for fertilization to occur. Causes can include hormonal problems, infections, varicocele, or lifestyle habits like smoking and alcohol use.

• Poor Sperm Motility or Morphology

Sperm motility refers to how well the sperm moves. Morphology is about their shape. If sperm can’t swim properly or are abnormally shaped, it becomes difficult to reach and fertilize the egg.

• Hormonal Imbalances

Hormones like testosterone are essential for sperm production. Imbalances in these hormones due to conditions like hypogonadism or thyroid problems can lead to infertility.

• Varicocele

This is an enlargement of the veins within the scrotum, similar to varicose veins. It can increase the temperature in the testicles and affect sperm production and quality. Fortunately, it’s a treatable cause of male infertility.

• Infections and STIs

Infections such as mumps, sexually transmitted infections (STIs), or inflammation of the reproductive organs can interfere with sperm production and transport.

• Lifestyle Factors

Smoking, drinking too much alcohol, being overweight, stress, and exposure to environmental toxins (like heavy metals and radiation) can all harm sperm health. These lifestyle choices are among the leading infertility causes in men.

Major Causes of Infertility in Women

Now let’s look at the major causes of infertility in men and women from the female side. A woman’s ability to conceive depends on several factors, especially her ovulation cycle and reproductive health.

• Ovulation Disorders (e.g., PCOS)

Polycystic Ovary Syndrome (PCOS) is one of the most common causes of ovulation problems. When ovulation doesn’t happen regularly, the chances of conception drop. Other hormonal disorders hypothalamic amenorrhea, premature ovarian insufficiency (POI), and hyperprolactinemia also disrupt ovulation. These conditions may result from stress, excessive exercise, or genetic factors, affecting fertility significantly.

• Endometriosis

This is when the tissue that lines the uterus grows outside it, often on the ovaries or fallopian tubes. It can cause severe pain and make it difficult for the egg and sperm to meet due to anatomical disarrangement or other factors. Endometrial implants may also trigger inflammation, scar formation, and pelvic adhesions, which further hinder fertility. In severe cases, it may damage ovarian reserve or distort pelvic anatomy, making natural conception more challenging.

• Blocked Fallopian Tubes

Fallopian tubes are the place where egg and sperm meet. Embryo formation occurs here, and after 3-4 days, the embryo shifts from tubes to uterus for implantation. If they’re blocked due to infections, past surgeries, or ectopic pregnancies, it can prevent the egg and sperm from meeting. Common causes include pelvic inflammatory disease (PID), tuberculosis of the reproductive tract, or endometriosis. Blockages may be partial or complete and often go unnoticed until a fertility evaluation is done.

• Uterine Abnormalities

Structural problems in the uterus, like fibroids, polyps, or a misshapen uterus, can prevent implantation or lead to miscarriage. Congenital conditions like a septate uterus or acquired conditions like intrauterine adhesions can interfere with embryo implantation. Some abnormalities can also alter menstrual flow or increase the risk of preterm labor.

• Hormonal Imbalances

Like men, women also need a delicate hormonal balance. Problems with the thyroid, excessive prolactin, or irregular estrogen levels can affect the menstrual cycle and ovulation. Disorders like hypothyroidism, hyperthyroidism, or adrenal dysfunction can disrupt the hypothalamic-pituitary-ovarian axis. These imbalances often present with irregular cycles, missed periods, or symptoms like acne, hair loss, or weight gain.

• Age-Related Decline

A woman’s fertility naturally declines with age. After 35, egg quality and quantity start decreasing significantly, making conception more difficult. In addition to reduced egg reserve, older eggs are more prone to chromosomal abnormalities. This increases the risk of miscarriage or conditions like Down syndrome, often necessitating fertility preservation or assisted reproduction.

• Lifestyle and Environmental Factors

Poor diet, being underweight or overweight, high-stress levels, and exposure to environmental toxins can all contribute to female infertility.  Smoking, alcohol, pesticides, plastics (like BPA), and long-term exposure to heat or radiation may impair ovulation and egg quality. Adopting a healthy lifestyle and minimizing exposure can significantly improve fertility outcomes.

Shared or Unexplained Causes

Sometimes, both partners may have minor issues that together affect fertility. In other cases, no clear reason can be found despite thorough testing. This is called unexplained infertility and can be frustrating, but many couples still conceive with the right support.

Some of these shared causes may include autoimmune disorders, subtle genetic issues, or mild hormonal imbalances that do not show up in standard tests. Unexplained infertility can also be related to poor egg or sperm quality that may not be visible through basic diagnostics. In such cases, lifestyle changes and advanced medical approaches such as IVF may be recommended. Even without a diagnosis, there are still many successful fertility outcomes through monitoring and fertility treatment strategies tailored to the couple’s needs.

These cases still fall under the broad umbrella of the major causes of infertility in men and women, even if no exact cause is found.

When to Seek Medical Help

Knowing when to get professional help is crucial. Here are some general guidelines:

• Women under 35: After 12 months of trying.
• Women over 35: After 6 months of trying.
• Women over 40: Seek help right away.
• If you know of a condition that affects fertility (like PCOS or endometriosis), don’t wait—get evaluated early.

Seeking help early ensures timely interventions and increases the chances of successful treatment. Fertility declines with age, and delayed diagnosis may limit treatment options. A fertility specialist can help assess the situation, suggest necessary tests, and recommend lifestyle or medical solutions based on your specific condition. Whether it’s hormonal support, ovulation tracking, or assisted reproductive techniques, the sooner you begin, the better your chances of success. Don’t let the uncertainty hold you back. Infertility is more common than most people think, and support is available.

Consulting a fertility specialist can provide insights, diagnosis, and a proper plan for moving forward.

Diagnostic Tests and Evaluations

To check your fertility health, the fertility experts will evaluate you with certain tests and analyse your fertility health.

For Men:

• Semen analysis (to check sperm count, motility, and shape)
• Hormone testing (eg. Diabetes Mellitus, Hypertension)
• Ultrasound (to look for varicocele or other abnormalities)

For Women:

• Hormone tests (AMH, FSH, LH, estrogen, prolactin, thyroid)
• Ultrasound (to check ovaries and uterus)
• HSG (to check if the fallopian tubes are patent)
• Ovulation tracking

Advanced tests may include genetic screening, or laparoscopy in case of suspected endometriosis or pelvic adhesions. Depending on the findings, couples may be advised to try natural methods, timed intercourse, or begin fertility treatment such as IUI or IVF. These evaluations help identify not just the cause but also the most effective treatment path. Personalized care based on thorough testing often leads to better outcomes and helps ease the emotional burden of infertility.

In cases of unexplained or prolonged infertility, doctors may suggest fertility treatment like IUI (Intrauterine Insemination), IVF (In Vitro Fertilization), or ICSI (Intracytoplasmic Sperm Injection). These fertility treatment methods offer hope when natural conception isn’t happening.

Understanding the major causes of infertility in men and women is the first step in taking control of your fertility journey. Whether it’s low sperm count, ovulation disorders, or lifestyle issues, many of these causes are treatable with timely intervention.

Remember:

• Male infertility and female infertility are both equally important.
• Lifestyle changes can make a big difference.
• Don’t delay seeking help if you’re struggling to conceive.

Infertility may feel overwhelming, but there’s hope. With the right diagnosis and support, many couples achieve their dream of parenthood. If you’re facing fertility challenges, don’t lose hope. Consult a trusted expert centers like Sudha Fertility Centre have helped thousands of couples take confident steps toward parenthood with compassionate care and advanced technology. Let’s break the silence, spread awareness, and support one another in understanding the major causes of infertility in men and women.