Causes of Infertility: An Overview


Quick look at causes of infertility


Infertility is a medical condition defined by the inability to achieve pregnancy after one year of regular, unprotected sexual intercourse. However, many think a workup is reasonable after six months if a woman is 35 or older, has underlying risk factors or is stressed about not conceiving.
Causes of infertility include a variety of conditions affecting the reproductive systems of men and women and often relates to problems with both at the same time.
Treatment for infertility can include lifestyle adjustments, but is more likely to be successful with oral medications and insemination, or advanced medical treatments such as in vitro fertilization (IVF).

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What is infertility?

Infertility is the inability to get pregnant after one year of regularly having unprotected sexual intercourse. In order for pregnancy to occur naturally, a woman must release a healthy egg from her ovaries at just the right time for it to be fertilized by the healthy sperm of a man. Then the fertilized egg, called an embryo, must pass from the fallopian tube and implant in the uterus.

When a couple is struggling to conceive, it is usually because something is going wrong in that natural process. In women, infertility may be caused by hormonal imbalances affecting ovulation (the release of the egg) or by conditions affecting the physical structure of the reproductive organs such as endometriosis or blocked fallopian tubes. In men, infertility can be caused by issues related to poor sperm health or quantity, a blockage or erectile dysfunction. Genetic issues can also cause infertility in both men and women.

Infertility is common, affecting 1 in 8 couples in the United States. According to the American Society for Reproductive Medicine, about one-third of infertility cases are due to male factors and one-third are due to female factors. The remaining third are caused by a combination of male and female factors or diagnosed as unexplained infertility.

Unexplained infertility

Around 20 percent of couples receive a diagnosis of unexplained infertility. This means that testing and examination are unable to reveal a precise cause of infertility. Fertility testing is able to detect the major causes of infertility such as sperm count and ovulation disorders, but testing is limited in identifying more subtle issues such as poor egg quality. Additionally, hysterosalpingograms (HSGs), a type of X-ray exam used to diagnose infertility, can falsely indicate that a patient’s tubes are normal when they are actually damaged. Couples diagnosed with unexplained infertility are often still great candidates for fertility treatments despite the fact that the cause of their struggle to conceive cannot be pinpointed.

Related Information: Fertility Treatments Overview

Causes of infertility in women


A woman’s fertility naturally declines as she gets older and approaches menopause. Research has demonstrated that a woman’s fertility peaks in her early 20s and begins to slowly decline after that, with a more dramatic reduction occurring after age 35. This reduction is due to several factors including reduced egg quality, age-related hormone changes affecting ovulation and decreased function of the uterus.

Ovulation disorders

Every woman is born with a finite number of eggs, and while almost 800 eggs are lost each month, usually only one makes it to a point where it is released by the ovaries for fertilization in a process called ovulation. This process relies on a delicate balance of hormones in her body. If the released egg is not fertilized by a man’s sperm, it breaks down along with blood and tissue from the lining of the uterus in a process called menstruation. If a woman is having infrequent or irregular menstruation, it may indicate that she is not ovulating properly.

One common contributor to ovulation disorders is polycystic ovary syndrome (PCOS), which affects 5 to 20 percent of women of childbearing age. PCOS is a hormonal imbalance with extra testosterone (“male hormone”), making it hard for an egg to develop to a size where it can be released. Women with this condition are told they have cysts on their ovaries, when in reality these aren’t usually worrisome cysts (being relatively small), but are just a fraction of the 800 eggs that would be lost naturally if her hormones were balanced. The hormonal imbalance in PCOS can lead to poor egg quality along with other side effects such as weight gain, acne and excessive hair growth.

Tubal disease or blockage

The fallopian tubes are a pair of thin tubes connecting the ovaries to the uterus. If a woman is affected by tubal disease, it means that one or both of her fallopian tubes are partially or fully blocked or damaged in some way. Blockages may be due to an infection, previous trauma such as surgery or abdominal disease, or a birth defect.

The blockage can prevent the woman’s released egg from arriving in the fallopian tube where fertilization by sperm takes place. It also can prevent transport of the fertilized egg (embryo) to the uterus (womb) and therefore stop pregnancy from occurring. Tubal damage is important beyond just whether sperm and egg can find each other—if tubes are damaged, this can prevent an embryo from traveling back to the uterus and can result in ectopic pregnancy.


Endometriosis is a chronic disorder in which the tissue that lines the uterus, called the endometrium, spreads outside of the uterus and onto surrounding pelvic tissues and organs. The tissue continues to behave as it would within the uterus, getting thicker and bleeding as it does during menstruation. This can cause significant pain and discomfort in addition to making it more difficult for a woman to conceive, particularly if the case is severe.

Uterine fibroids, polyps & other abnormalities

Female infertility may be caused by other problems with the uterus aside from endometriosis. These include fibroids, polyps and other abnormalities such as scarring and structural defects that can be present from birth. Abnormalities may also be caused by surgery or disease.

Among these problems, polyps are the most common, affecting up to 15 percent of women with infertility. Polyps are growths of the lining of the uterus that didn’t stop growing when they were supposed to. Though unlikely, they can progress to cancer and are often diagnosed and treated with hysteroscopy.

Uterine fibroids are also common, affecting 5 to 10 percent of women diagnosed with infertility. Fibroids are noncancerous growths from the muscle of the uterus, and they often do not cause any symptoms. They can make both conceiving and pregnancy more difficult, depending on their number, size and location.

Lifestyle and environmental factors

A range of other factors can contribute to infertility in women. Because of the balance of hormones required for proper reproductive functioning, certain lifestyle habits and environmental factors may negatively impact a woman’s chances of getting pregnant. These include:

  • Obesity and being overweight (particularly if ovulation stops)
  • Being underweight (particularly if ovulation stops)
  • Smoking
  • Drugs & alcohol
  • Environmental toxins such as lead or radiation from medical equipment.

Related Information: Fertility Testing for Women

Causes of infertility in men

infertility | Positive Steps Fertility | Madison, MS | concerned man looking out windowAbout 40 percent of infertility cases involve issues with the male partner, either as the sole cause or a contributing factor. Male-factor infertility usually has to do with the quantity and quality of sperm in a man’s semen. Listed below are some of the more common conditions that can negatively impact fertility in men.

Anatomical causes

After sperm are produced in a man’s testicles, they travel through small tubes to mix with semen before being ejaculated from the penis. If something in a man’s anatomy blocks the flow of sperm to the semen, it may result in low sperm count or poor sperm quality, making it more difficult for pregnancy to occur.

One of the more common anatomical causes of male infertility is a varicocele, which is an enlarged vein within the scrotum. It is thought that the enlargement can impede blood flow and raise the temperature within the scrotum, causing reduced sperm production and poorer sperm quality.

Varicoceles are very common and do not always cause infertility in men. It is estimated that about 15 percent of the male population have varicoceles (including Dr. Parry – so men who have one are not alone).

Other physical defects contributing to male infertility include testicular torsion (twisting and swelling of a testicle which may cause permanent damage), retrograde ejaculation, undescended testicle, and damage or blockage in the ducts that carry sperm to the semen.

Erectile dysfunction (impotence)

Erectile dysfunction, or impotence, is when a man is unable to get or maintain an erection for intercourse. This can be due to underlying disorders such as diabetes or heart disease but may also occur due to psychological issues including depression and anxiety. Lifestyle factors such as drug and alcohol abuse can also affect a man’s ability to obtain and sustain an erection. 

Hormonal disorders

The production of healthy sperm requires a proper balance of sex hormones in a man’s body. Disorders affecting the thyroid and pituitary glands, for example, can negatively impact the amount of testosterone and other reproductive hormones in a man’s body. This can in turn have a negative impact on sperm production.

Lifestyle and environmental factors

Unhealthy lifestyle habits have been shown to negatively impact male fertility. Fertility experts also theorize that activities that increase the temperature of the scrotum, such as prolonged sitting, wearing tight pants or underpants, using a laptop computer and saunas and hot tubs, may decrease sperm production. Other lifestyle and environmental factors that can affect male fertility include:

  • Poor diet
  • Obesity
  • Smoking
  • Drugs & alcohol
  • Excessive stress
  • Exposure to environmental toxins such as industrial chemicals, lead or radiation.

Related Information: Fertility Testing for Men

Genetic causes of infertility in men and women

Certain genetic abnormalities may be carried by one or both partners and passed onto the developing embryo or fetus. These can result in implantation failure or miscarriage. Couples with a family history of genetic disorders may benefit from preimplantation genetic screening and diagnosis (PGS/PGD) during IVF, which can identify abnormal chromosomes in embryos.

Related information: Preimplantation Genetic Screening & Diagnosis

Infertility treatment

Treatment for infertility varies depending on diagnosis and may include conservative measures such as lifestyle modification and adopting healthy habits. In other cases, surgical procedures or medications to correct underlying conditions can restore a couple’s ability to naturally conceive. Advanced reproductive technologies (ART) such as IVF are recommended for more severe or persistent cases in which lower tech approaches are less likely to lead to a successful outcome.

Related Information: Fertility Treatments

Next steps: Diagnosing and treating infertility at Positive Steps Fertility

Our fertility practice is fully equipped to diagnose and treat infertility in men and women. Of note, Dr. Parry pioneered the Parryscope technique and approach, allowing for accurate, gentle, fast, single-visit fertility testing where a woman gets results as the procedure is being performed. We can help you get answers quickly and help you decide the best way to efficiently approach building the family you want.