Medically reviewed by Dr. Griffin M, MBBS, MS (General Surgery), MCh (Urology). Specialist in Urology, Andrology & Kidney Transplant Surgery | Last reviewed: October 2026
Infertility can occur due to various factors affecting the reproductive health of both men and women. In women, common causes include hormonal imbalances, ovulation disorders, blocked fallopian tubes, endometriosis, and age-related changes in fertility. In men, low sperm count, poor sperm motility, abnormal sperm shape, and hormonal problems may affect the ability to conceive. Certain medical conditions, previous infections, lifestyle habits, stress, and environmental factors can also contribute to fertility challenges.
Sometimes, couples experience unexplained infertility, where the exact cause remains unclear despite medical investigations. Understanding the possible causes of infertility helps couples take informed steps towards diagnosis and treatment. Consulting a fertility specialist can help identify underlying concerns and provide personalised guidance based on each partner’s reproductive health and individual needs.
What Does Infertility Mean?
In medical terms, a couple is considered infertile when pregnancy has not happened after 12 months of regular, unprotected intercourse. When the woman is 35 or above, doctors usually advise getting evaluated after 6 months, since fertility changes faster with age.
It helps to know the two main types.
- Primary infertility applies to couples who have never conceived.
- Secondary infertility applies to couples who have conceived before, whether the pregnancy ended in a birth or a miscarriage, but are now finding it hard to conceive again. Many couples are surprised by this. A past pregnancy feels like proof that everything works. But age, weight, infections, new medicines or surgeries can change things over the years.
How Common Is Infertility?
Infertility is more common than many people realise. The World Health Organization (WHO) estimates that approximately one in six adults worldwide experiences infertility during their lifetime. In India, many couples experience difficulty conceiving, although the prevalence varies across regions and populations.
Infertility may be associated with female reproductive factors, male reproductive factors, a combination of both, or unexplained causes. This is why fertility evaluation should involve both partners rather than focusing on only one person. Early assessment can help identify potential causes and guide couples towards suitable treatment options based on their individual needs.
Causes of Infertility in Men
For a long time, infertility was seen as a woman’s problem. That belief delays treatment for many couples. Male factors contribute to a large share of cases, and most of them can be checked with a simple test.
- Problems with sperm. Three things matter most: how many sperm are present (count), how well they move (motility), and how they look (morphology). The WHO reference value for a normal sperm concentration starts at about 16 million per millilitre of semen. A lower number may reduce the chance of conception, but it does not close the door. Movement and shape carry equal weight in the overall picture.
- Varicocele. This means enlarged veins in the scrotum. It is seen in about 35 to 40 percent of men evaluated for primary infertility. Blood pooling in these veins can raise the temperature of the testicles, and sperm do not make well in a warm environment. Most men feel nothing, so it often goes unnoticed until a doctor examines the area.
- Infections. Infections of the urinary tract, prostate or epididymis can affect sperm quality or block the passage of sperm. Mumps involving the testicles in adulthood is another recognised cause.
- Blockages. Some men produce sperm normally, but the sperm cannot travel out. Blockages can happen after infection, injury or surgery, and some men are born with a missing or blocked sperm duct. A semen report in such cases may show no sperm at all.
- Hormonal imbalance. Testosterone, FSH, LH and prolactin work like a team to keep sperm production running. When one of them is off, the whole process suffers. A point worth repeating: testosterone injections, gels and bodybuilding steroids can suppress natural sperm production, sometimes for many months. Men using them should tell their doctor before planning a pregnancy.
- Genetic conditions. Klinefelter syndrome and missing portions of the Y chromosome can lead to very low or absent sperm counts. Genetic tests are usually reserved for men whose counts are severely low.
- Sexual function problems. Erectile difficulty, premature ejaculation, or retrograde ejaculation, where semen flows backward into the bladder, can make conception hard even when sperm are healthy.
- Earlier health events. An undescended testicle in childhood, testicular injury or twisting, hernia or groin surgery, and cancer treatments such as chemotherapy or radiotherapy can all affect fertility later on.
Causes of Infertility in Women
Evaluating the female partner is just as important. These are the most common reasons found.
- Ovulation disorders. Pregnancy needs an egg to be released regularly. Polycystic ovary syndrome (PCOS), thyroid disease, raised prolactin and early decline of ovarian function can all disturb this. Irregular or missing periods are often the first hint.
- Blocked or damaged fallopian tubes. The tubes are the pathway where sperm meets egg. Pelvic infections, endometriosis, earlier abdominal surgery and, in some cases, genital tuberculosis can scar or block them.
- Uterine and cervical factors. Fibroids, polyps, internal scar tissue and structural variations like a uterine septum can make it harder for an embryo to implant or for a pregnancy to continue.
- Endometriosis. Tissue similar to the lining of the womb grows outside the uterus. It can cause painful periods and pelvic pain, and it may affect the ovaries and tubes.
- Age. A woman is born with a fixed number of eggs. Their number and quality gradually fall, and the change is faster after 35. There is nothing anyone did wrong here. It is simply how the body works, and it is the main reason doctors suggest earlier testing for women in their mid thirties.
Combined and Unexplained Infertility
Sometimes both partners have a small issue. Each one alone might not stop conception, but together they lower the chance in any given month.
In some couples, every test comes back normal. This is called unexplained infertility. It can feel more upsetting than a clear diagnosis, since there is no obvious thing to fix. Yet many of these couples do go on to conceive, either naturally over time or with treatments such as IUI or IVF, as guided by their doctor.
Lifestyle and Environmental Factors
Habits rarely act alone, but they can add to an existing problem.
- Smoking reduces sperm count and movement and can affect egg health in women.
- Heavy drinking can lower testosterone and sperm quality.
- Being overweight or underweight disturbs hormone balance in both partners.
- Ongoing stress and poor sleep can alter hormones and reduce intimacy.
- Heat exposure, such as frequent hot tubs or saunas, may affect sperm. The evidence on laptops and mobile phones is weak, so there is no need to worry too much about them.
- Workplace exposure to pesticides, solvents or heavy metals may harm fertility.
- Recreational drugs and some prescription medicines can interfere with sperm production or ovulation.
There is a hopeful side here. Sperm takes about three months to mature, so healthy changes made today can show up in a semen report a few months from now.
Signs of Infertility
Infertility does not always cause noticeable symptoms, and difficulty getting pregnant may be the first sign. However, certain changes in reproductive health may indicate an underlying fertility problem.
Common signs of infertility in women:
- Irregular or missed menstrual periods
- Very painful or heavy periods
- No periods for several months
- Pain during sexual intercourse
- Symptoms of hormonal imbalance, such as excessive facial hair or persistent acne
- A history of endometriosis, pelvic infections, or reproductive health conditions
Common signs of infertility in men:
- Difficulty maintaining an erection or ejaculating
- Reduced sexual desire
- Pain, swelling, or a lump in the testicles
- Changes in semen volume
- A history of testicular injury or reproductive infections
How Do Doctors Find the Cause?
It starts with a long, honest conversation about your health history, medicines, habits, past infections, surgeries and how long you have been trying. After that, a few tests help.
For men, the semen analysis is the first step. It is painless, quick and very informative. You will be asked to abstain for two to seven days beforehand. If the result is abnormal, it is usually repeated after a few weeks because sperm quality can vary from sample to sample. Depending on the findings, doctors may also suggest:
- Blood tests for testosterone, FSH, LH and prolactin
- A scrotal ultrasound with Doppler to look for varicocele
- A urine test after ejaculation to check for retrograde ejaculation
- Genetic testing in selected cases
For women, the tests commonly include hormone and thyroid blood work, an ovarian reserve test such as AMH, a pelvic ultrasound, and an imaging test to check whether the fallopian tubes are open.
Many doctors recommend the semen test early, since it is simple and can save couples several months of uncertainty.
When Should You See a Doctor?
You do not need to wait until you feel overwhelmed to seek help. Consider consulting a fertility specialist if:
- You have been trying to conceive for an extended period without success.
- The woman has irregular or absent menstrual periods.
- Either partner has a known reproductive health concern, such as a varicocele, a history of undescended testicles, or a previous pelvic infection.
- Either partner has undergone cancer treatment that may affect fertility.
- The woman has experienced repeated miscarriages.
- Either partner experiences difficulties with erection or ejaculation.
Seeking medical advice early does not necessarily mean something is seriously wrong. It allows potential fertility concerns to be identified sooner and gives couples more time to understand their options and plan appropriate treatment.
Treatment Options
The right treatment depends on the cause, the age of both partners and how long a couple has been trying to conceive. Commonly used approaches include:
- Lifestyle changes such as quitting smoking, reducing alcohol and improving sleep and body weight
- Medicines to correct hormone imbalances, treat infections or support ovulation
- Surgery, such as varicocele repair or correction of a blocked sperm duct, when a structural cause is found
- Assisted reproduction such as IUI, IVF and ICSI, where a single sperm is injected directly into an egg
Outcomes vary from one couple to another, and no treatment can be guaranteed to work. This information is for general awareness and is not a substitute for medical advice. A consultation with a qualified doctor, after the necessary tests, is needed to decide which approach is suitable for you.
Conclusion
Infertility can have many causes, and there are many ways forward. Whether the cause lies with the man, the woman, both partners, or no clear cause is found, the first step is the same: evaluation of the couple together, without blame. Many couples find that understanding what is happening brings some relief.
If you have been trying to conceive for a while, it is reasonable to speak to a qualified doctor. A consultation and the appropriate tests can help identify possible causes and the options available to you. This information is for general awareness and is not a substitute for medical advice.
Read More: Is Infertility Curable?
