Contact Us Site Map Search
Reproductive Health Technologies Project  
Leadership Transition Abortion Contraception STDs Fertility News & Publications About Us
  Print this page  

Causes of male infertility
Causes of female infertility

Infertility is clinically defined as the inability to conceive naturally after one year of frequent, unprotected intercourse.  Approximately 7.3 million people in the U.S., 10 to 15 % of the population is infertile.1Infertility has many causes, often compounded by physical, behavioral and environmental health factors.  About 30 % of infertility can be caused by male complications, 30% by female complications, and 30% by a combination of the two of which 20% remains unexplained.2

Causes of male infertility
The most common causes of male infertility arise from impaired sperm production, function and delivery; behavioral and lifestyle factors; and harmful environmental exposures. 

Male infertility gradually declines in men older than 35.  Impaired sperm morphology (shape) and motility (movement) and low sperm count are the most common causes of male infertility.  A normal sperm count is 20 million or more sperm per milliliter of semen.  A sperm count of less than 10 million sperm per milliliter is considered low and may indicate infertility. If a man’s sperm count is below 5 million per milliliters of semen, genetic factors are suspected.3

Sperm dysfunction can be caused by physical abnormalities, such as an undescended testicle, that raise the temperature of the testes higher than the sensitive range required for normal sperm production.  Low testosterone due to genetic defects or malfunction in the GnRH, FSH and LH pathway can also decrease sperm production and function. Chemotherapy and radiation treatment for cancer can also severely damage sperm and contribute to infertility.

Repeated cases of sexually transmitted infections inflame the testicles, prostate and urethra and cause scarring and blockage of sperm.   Erectile and ejaculation dysfunction, associated with various health conditions such as cystic fibrosis and complications following urogenital surgery, can also impair the delivery of sperm. 

Behavioral and Lifestyle3

  • Emotional, psychological or relationship stress can interfere with the GnRH, FSH and LH pathway, and can contribute to decreased sperm production.
  • Vitamin deficiencies as well as obesity are also associated with male infertility.  
  • Men who use alcohol and drugs in excess, especially tobacco and anabolic steroids, tend to have lower sperm counts.  Marijuana and cocaine use may also contribute to temporary infertility.

Exposure to harmful environmental elements can lead to infertility.

  • Frequent use of laptops near the testicles4 as well as saunas and hot tubs can all raise the temperature of the testes and reduce sperm function.
  • A recent study also found a relationship between increased cell phone use and reduced sperm count.5
  • New research is emerging linking male infertility with pesticide, lead and other chemical exposure.  Many of these synthetic chemicals are endocrine disruptors that interrupt normal hormone functioning.  For more information on environmental contaminants and infertility please click here.

Causes of female infertility
The most common causes of female infertility arise from reproductive organ malfunction and abnormalities, hormonal imbalances, and behavioral and lifestyle factors.

Female fertility begins to decline around age 32. Of the 2 million follicles present at birth, only about 400 will mature and release ova over the course of the woman’s reproductive life.  Once this reserve is depleted, a woman can no longer have children naturally.

Inflammation and scarring of the fallopian tubes (salpingitis), and the uterus (endometriosis) can result in female infertility.  These disorders can be caused by untreated sexually transmitted infections, tumors and scar tissue following pelvic surgery. 

Disruptions in the GnRH, FSH and LH pathway, triggered by hormonal imbalances in androgen (polycystic ovary syndrome or PCOS) and prolactin, can disrupt normal ovulation and also cause infertility. 

Medical conditions such as thyroid problems, cancer and its treatment with radiation, chemotherapy and/or surgery, and early menopause (premature ovarian failure) also contribute to female infertility.  

Behavioral and Lifestyle3

  • Women who use alcohol and tobacco greatly reduce their chances of becoming pregnant and increase their risk of miscarriage.
  • Some studies have shown a decrease in female fertility with increased caffeine consumption.6
  • Obesity and a sedentary lifestyle as well as being underweight and excessive exercise are all associated with a decline in fertility. 
  • Vitamin deficiencies, often seen in strict vegetarians, can complicate conception. 

A large number of animal studies have been published linking environmental contaminants, synthetic chemicals and endocrine disruptors to possible irregularities in ovulation, menstruation, oocyte integrity and embryonic development.  The evidence linking environmental contaminants and infertility continues to mount. For more information please click here.

1 Chandra A, Martinez GM, Mosher WD, Abma JC, Jones J. Fertility, family planning, and reproductive health of U.S. women: Data from the 2002 National Survey of Family Growth. National Center for Health Statistics. Vital Health Stat 23(25). 2005.  Available at:  http://www.cdc.gov/nchs/about/major/nsfg/abclist_i.htm#infertility  Accessed February 2008.

2 American Society for Reproductive Medicine.  Frequently Asked Questions About Infertility.  Available at:  http://www.asrm.org/Patients/faqs.html#Q2: Accessed February 2008.

3 Mayo Clinic.  Infertility.  Available at: http://www.mayoclinic.com/health/infertility/DS00310/DSECTION=3 .  Accessed February, 2008.

4 Sheynkin Y, Jung M, Yoo P, Schulsinger D, Komaroff E.  Increase in scrotal temperature in laptop computer users.  Human Reproduction 2004.  Available at http://humrep.oxfordjournals.org/cgi/content/abstract/deh616v1. Accessed March 2008.

5 Agarwal A, Deepinder F, Sharma RK, Ranga G, Li J. Effect of cell phone usage on semen analysis in men attending infertility clinic:  an observational study.  Fertility and Sterility 2008; 89:  124-128.

6 Bolúmar F,Olsen J, Rebagliato M, Bisanti L, and European Study Group on Infertility and Subfecundity.  Caffeine Intake and Delayed Conception: A European Multicenter Study on Infertility and Subfecundity. Am. J. Epidemiol 1997; 145: 324-334.




back to top

Abortion | Contraception | STDs | Fertility | News & Publications | About Us
Contact Us | Site Map