Heredity, environment, and lifestyle can all play a part when it comes to what causes infertility in men and women. Here's what hopeful parents should know.

October 03, 2005
negative pregnancy test
Credit: Shutterstock

Having a baby is a happy occasion that many couples look forward to. Yet more than five million Americans, both men and women, have problems with infertility.  In fact, about 35 percent of fertility cases can be traced to a problem in the man, and an additional 20 percent to a problem in both partners.

If you're trying to get pregnant now, or planning to in the future, it's wise to identify any potential risk factors you or your partner may have, and to tell your doctor right away. The sooner you detect, address, and treat problems that may affect fertility, the better your chances of achieving a successful pregnancy. You should also always tell your doctor if you've had a history of multiple miscarriages, painful menstrual cycles that require medication for pain relief, or abnormal Pap smears that have resulted in surgical treatment, as these factors can also affect fertility.

To get you started on the right foot, here are a few of the more common health factors and conditions that can affect a woman's ability to ovulate, conceive, or carry a pregnancy to term, as well as risk factors that may contribute to male infertility.

Causes of Infertility in Women

Being Over or Under Weight

Body fat levels that are 10 to 15 percent above normal can overload the body with estrogen, throwing off the reproductive cycle. Body fat levels 10 to 15 percent below normal can completely shut down the reproductive process.

Having a hormonal imbalance

Irregularities in the hormone system (characterized by irregular menstrual cycles or short, long, or heavy periods) can affect ovulation.

Having an autoimmune disorder

Diseases such as lupus, diabetes, thyroid disease, and rheumatoid arthritis can interfere with fertility.

Taking medication

Antidepressants, antibiotics, painkillers, and other drugs used to treat chronic disorders may cause temporary infertility.

Using tobacco or alcohol

Smoking may increase the risk of infertility in women; and even moderate alcohol consumption (as few as five drinks a week) can impair conception.

Being exposed to occupational or environmental hazards

Prolonged exposure to high mental stress, high temperatures, chemicals, radiation, or heavy electromagnetic or microwave emissions may reduce a woman's fertility.

Fallopian tube disease

Fallopian tube disease accounts for about 20 percent of infertility cases treated, according to RESOLVE: The National Infertility Association. If a doctor suspects a problem, he or she can perform a hysterosalpingogram -- an X-ray that can evaluate the condition of the uterus and determine if the fallopian tubes are obstructed. Since tubal scarring or blockage is often caused by sexually transmitted diseases (STDs), pelvic inflammatory disease, or certain surgeries, alert your doctor if you've had:

  • An STD, such as gonorrhea, syphilis, or chlamydia
  • Pelvic pain, unusual vaginal discharge, and/or bleeding, with or without a fever
  • Pelvic surgery for a ruptured appendix, ovarian cysts, or an ectopic pregnancy (a pregnancy that takes place outside of the uterus, usually in the fallopian tubes)


Endometriosis is a condition in which tissue from the uterine lining grows outside the uterus, on the ovaries, fallopian tubes, bladder, and/or bowel. Research indicates that it accounts for between 5 and 30 percent of female infertility. In some cases, women with endometriosis have no painful symptoms. In these instances, the condition can only be confirmed with an outpatient surgical procedure called a laparoscopy. Several factors may contribute to infertility, including:

  • Scar tissueRigid webs of scar tissue may form between the uterus, ovaries, and fallopian tubes, preventing the transfer of the egg to the fallopian tubes.
  • CystsEndometrial cysts may grow inside the ovaries and prevent the release of the egg or its collection by the fallopian tube.
  • Poor egg implantationEndometriosis may prevent the fertilized egg from adhering to the uterine wall.

Early detection of the condition is key to its successful control and to preserving fertility, so tell your doctor if you've had:

  • A family history of endometriosis
  • Painful menstrual cramps or pain at ovulation
  • Extremely heavy menstrual flow
  • Diarrhea or painful bowel movements, especially around your period
  • Painful sexual intercourse

Sexually transmitted diseases

More than 65 million Americans, including teenagers, are infected with at least one STDs. Some STDs are asymptomatic and lie undetected in women. (For instance, 70 percent of women with chlamydia show no symptoms and consequently don't seek treatment.) The bad news is that STDs can lead to tubal scarring, ectopic pregnancy, other reproductive problems, and ultimately infertility if left untreated. To reduce this risk:

  • Use latex condoms to stop diseases from spreading
  • Consider that people with multiple sex partners are at the highest risk for STDs
  • Detect and treat infections early if possible (both partners should be treated if either has an infection)

Causes of Infertility in Men

Being a smoker

Smoking impairs the ability of sperm to move (its motility).

Using alcohol

Having more than one or two drinks a day can affect the quality and quantity of sperm, lower testosterone levels, and contribute to erectile dysfunction.

Taking illegal drugs

Cocaine or heavy marijuana use may temporarily reduce the number and quality of sperm by as much as 50 percent.

Taking prescription drugs

Some medications, such as those for ulcers or psoriasis, can slow or prevent the production of sperm.

Being exposed to toxic substances or hazards on the job

Chronic exposure to elements such as lead, cadmium, mercury, hydrocarbons, pesticides, radioactivity, and X-rays may have an impact on sperm count and quality.

Exposing genitals to heat

The frequent use of saunas, steam rooms, hot tubs, whirlpools, and hot baths can temporarily impair sperm production and reduce sperm count.

Having certain conditions or illnesses

Men with a history of prostatitis or genital infection, mumps after puberty, surgery on their hernia, undescended testicles, or scrotal varicose veins (varicocele) may also experience a decrease in fertility.

Sources:; RESOLVE: The National Infertility Association; The Couple's Guide to Fertility by Gary S. Berger, MD, Marc Goldstein, MD, and Mark Fuerst (Broadway Books, 2001); National Women's Health Information Center