Infertility is a medical condition affecting millions of people around the world, making it difficult or impossible for couples to conceive a child despite regular efforts. While the journey through infertility can feel isolating and overwhelming, many safe and effective treatments exist today, and understanding the causes and risk factors can help individuals and couples take the first steps toward building their families.

How Common Is Infertility Around the World?

Infertility is much more widespread than many people realize. According to research, approximately one out of every six people of reproductive age worldwide will experience infertility at some point in their lifetime. This means that millions of individuals and couples are facing similar challenges when trying to start or expand their families.^[3]

In the United States specifically, about one in five women between the ages of 15 and 49 who have never given birth struggle to get pregnant after trying for a year. Around one in twenty women experience difficulty conceiving again after having at least one successful pregnancy, a condition known as secondary infertility. Globally, researchers estimate that approximately 48 million couples live with infertility.^[1]

These statistics reveal that infertility affects a substantial portion of the population. It is not a rare condition, and people from all walks of life, backgrounds, and countries experience it. The emotional and physical toll can be significant, but knowing that others share this experience can provide some comfort and remind people that help and support are available.

What Causes Infertility?

Understanding the root causes of infertility is essential for anyone experiencing difficulty conceiving. Infertility can result from problems in either partner or a combination of factors affecting both. In fact, studies show that in about one-third of cases, infertility is related to female factors, in another third it involves male factors, and in the remaining third, it involves both partners or remains unexplained. Additionally, about 25% of couples dealing with infertility have more than one contributing factor.^[1]

For women, infertility can arise from a range of issues affecting the reproductive system. One of the most common causes involves problems with ovulation, the monthly release of an egg from the ovaries. When a woman does not ovulate regularly or at all, pregnancy becomes difficult or impossible. Conditions such as polycystic ovary syndrome, or PCOS, often interfere with normal ovulation. Disorders of the endocrine system, which includes glands like the hypothalamus and pituitary that produce reproductive hormones, can also disrupt ovulation.^[3]

Blocked or damaged fallopian tubes represent another significant cause of female infertility. The fallopian tubes are the pathways through which an egg travels from the ovary to the uterus, and where fertilization by sperm typically occurs. When these tubes are blocked—often due to untreated sexually transmitted infections, complications from unsafe abortion, postpartum infections, or previous abdominal or pelvic surgery—the egg and sperm cannot meet, preventing pregnancy.^[3]

Uterine disorders can also contribute to infertility. These may be inflammatory conditions like endometriosis, where tissue similar to the lining of the uterus grows outside the uterus, causing pain and scarring. Congenital abnormalities, such as a septate uterus (where a wall divides the uterine cavity), or benign growths like fibroids can interfere with implantation of a fertilized egg or carrying a pregnancy to term.^[3]

In men, infertility is most commonly caused by problems with sperm. This can include issues with ejaculation, the absence of sperm, or low sperm counts. Abnormalities in sperm shape, known as morphology, or movement, called motility, also play a role. When sperm cannot move effectively or are misshapen, they struggle to reach and fertilize the egg.^[3]

Sometimes, despite thorough testing and evaluation, doctors cannot identify a specific cause. This is called unexplained infertility, and it can be particularly frustrating for couples who are searching for answers.^[1]

Risk Factors That Increase the Likelihood of Infertility

Certain factors increase the risk of infertility for both men and women. One of the most significant risk factors is age. For women, fertility naturally declines with age, beginning in the early twenties and dropping more rapidly after age 35. Even with advanced fertility treatments like in vitro fertilization, or IVF, pregnancy becomes much less likely over the age of 42. For men, age starts affecting fertility closer to age 50.^[1][7]

Lifestyle choices and behaviors also play a crucial role. Smoking and using tobacco products significantly reduce fertility in both men and women. Smoking affects sperm quality in men and decreases the chances of conception in women. Excessive alcohol consumption similarly harms reproductive health, and current medical advice recommends avoiding alcohol entirely when trying to conceive.^[1][6]

Body weight is another important factor. Being overweight or obese, defined as having a body mass index, or BMI, of 30 or higher, reduces fertility. In women, being significantly underweight can also affect ovulation and the ability to conceive. Maintaining a healthy weight through balanced nutrition and regular exercise improves the chances of pregnancy.^[6]

Eating disorders such as anorexia nervosa and bulimia negatively impact fertility as well. These conditions disrupt normal bodily functions, including the hormonal balance necessary for reproduction.^[1]

Over-exercising can also lead to fertility problems. While staying physically active is important for overall health, excessive exercise—such as consistently running more than six to ten miles a day—can interfere with ovulation in women and reduce fertility in both sexes.^[1]

Sexually transmitted infections, or STIs, are a preventable cause of infertility. Several STIs, including chlamydia, can cause scarring and blockages in the reproductive organs if left untreated. Practicing safe sex and seeking prompt treatment for infections helps protect future fertility.^[6]

Environmental exposures can also harm fertility. Contact with certain pesticides, solvents, metals like lead, and other chemicals has been shown to affect fertility, particularly in men. Radiation therapy and chemotherapy used to treat cancer can also damage reproductive organs and reduce the ability to conceive.^[1]

Finally, high levels of stress can affect fertility. Stress impacts relationships and can lead to a loss of sex drive. In severe cases, stress may interfere with ovulation in women and sperm production in men. Finding healthy ways to manage stress is an important part of optimizing fertility.^[6]

Recognizing the Signs and Symptoms

The primary sign of infertility is the inability to become pregnant after a year of regular, unprotected sexual intercourse. For women aged 35 and older, this timeframe shortens to six months because fertility declines more rapidly with age. Many people with infertility do not experience any other obvious symptoms.^[1][2]

However, some individuals may notice physical symptoms that can be linked to underlying fertility issues. Women with infertility may experience irregular menstrual periods, meaning their cycles vary significantly in length or timing. Some women may have no periods at all, a condition called amenorrhea. Very painful periods can also be a sign of conditions like endometriosis, which affects fertility. Additionally, pelvic or abdominal pain may indicate problems with the reproductive organs.^[1]

In men, symptoms of hormonal problems may appear, such as changes in hair growth or sexual function. Issues with ejaculation or disorders affecting the penis can also signal potential fertility problems.^[1][2]

It is important to understand that many couples with infertility will eventually conceive, either naturally or with medical help. Recognizing these signs and seeking timely medical advice can make a significant difference in the journey toward parenthood.

Preventing Infertility: What You Can Do

While not all causes of infertility can be prevented, there are several steps individuals can take to protect and optimize their reproductive health. Maintaining a healthy lifestyle is one of the most effective strategies. This includes eating a balanced diet rich in nutrients, getting enough sleep, and managing stress through relaxation techniques, exercise, or counseling.^[18]

Achieving and maintaining a normal body weight is crucial. Being overweight, obese, or significantly underweight all negatively affect fertility. Losing weight or gaining weight to reach a healthy BMI can restore ovulation and improve the chances of conception.^[6]

Staying physically active is beneficial, but it is important to find balance. Regular exercise helps maintain fitness and supports reproductive health, but over-exercising can strain the body and disrupt normal hormonal function. Aim for moderate activity and avoid pushing the body to extremes.^[18]

Avoiding tobacco and limiting or eliminating alcohol consumption are essential steps. Smoking harms both egg and sperm quality and reduces the likelihood of successful conception. Similarly, drinking too much alcohol interferes with fertility. Medical guidelines recommend abstaining from alcohol when trying to conceive to minimize risks.^[6]

Protecting against sexually transmitted infections is another critical preventive measure. Using protection during sex and getting tested and treated for STIs can prevent damage to the reproductive organs and preserve fertility.^[6]

If you are planning to have children, it is wise not to delay. Female age is the number one factor determining fertility success, and the duration of infertility is the second most important factor. The earlier you start trying, the better your chances. If you experience regular menstrual cycles and have been trying for 12 months without success, or six months if you are over 35, seek help promptly. If your cycles are irregular, it is advisable to consult a healthcare provider right away.^[18]

Being informed and proactive about your health is empowering. Consider your body as something precious that requires care and attention. A healthy body supports a healthy reproductive system, and small changes today can make a big difference in your future fertility.

How Infertility Changes the Body: Understanding Pathophysiology

To understand infertility, it helps to know what must happen for a pregnancy to occur. Pregnancy is a complex process involving many steps. First, a woman’s brain must produce reproductive hormones that control the function of the ovaries. An egg must mature inside an ovary and then be released during ovulation. The fallopian tube must pick up the egg, and sperm must travel from the vagina, through the uterus, and into the fallopian tube. There, the sperm fertilizes the egg, creating an embryo. The embryo then travels through the fallopian tube to the uterus, where it implants into the uterine lining. If any of these steps fails, pregnancy cannot occur.^[1]

In women, disruptions in ovarian function are a common cause of infertility. A typical menstrual cycle lasts about 28 days, and regular, predictable periods usually indicate that ovulation is happening. When cycles are irregular or absent, ovulation may not be occurring. This can result from hormonal imbalances caused by conditions like PCOS or problems with the hypothalamus or pituitary gland, which regulate reproductive hormones.^[4]

When the fallopian tubes are blocked or damaged, the egg cannot meet the sperm. Blockages often result from infections, particularly untreated STIs, or scarring from surgeries or conditions like endometriosis. The tubes may also be affected by pelvic inflammatory disease, an infection of the reproductive organs that causes scarring and adhesions.^[3]

The uterus itself can have structural problems that interfere with implantation. Endometriosis causes tissue similar to the uterine lining to grow outside the uterus, leading to inflammation, pain, and scarring. Fibroids, which are non-cancerous growths in the uterus, can also prevent an embryo from implanting or developing properly.^[3]

In men, the most common pathophysiological issue is a problem with sperm production or delivery. The testicles may produce too few sperm, or the sperm may have abnormal shapes or poor movement. Sometimes the tubes that carry sperm from the testicles become blocked, preventing sperm from being ejaculated. Low levels of testosterone or other hormonal imbalances can also reduce sperm production.^[3]

Understanding these underlying mechanisms helps individuals grasp why certain treatments are recommended and why different causes require different approaches. Infertility is not simply one condition but rather a collection of potential problems affecting a carefully coordinated process.