Infertility has often been defined as failure to achieve pregnancy within 1 year of unprotected intercourse.

Delays in the time it takes to become pregnant or loss of pregnancy before term have been considered as evidence for sub-fertility.

Reproductive function has been shown to be sensitive to changes in the physical, psychosocial and chemical environments.

categories examples

Physical Light, temperature, radiation

Chemical Natural or synthetic

Biological Viruses, microorganism

Behavioral Stress, drug addiction

Socioeconomic Nutrition, habitat, occupation

Temperature:The enzymes required for the production of sperm are very sensitive to heat. Men who frequently use hot tubs, wear tight pants, sit at a desk all day, or stand in front of a hot stove may cause heating their testicles to such a degree that they can’t make sperm and get their partners pregnant. “The reason that the testicles should be about 4 degrees cooler than the normal body temperature,”

Being overweight: Body fat levels that are 10 to 15 percent above normal can overload the body with estrogen, throwing off the reproductive cycle.

Being underweight: Body fat levels 10 to 15 percent below normal can completely shut down the reproductive process

Age :By the time a woman is in her middle 30s, she has lost many of her viable eggs through menstruation and natural attrition. “The optimal age for a women to become pregnant, at least in terms of biology, is in her 20s,” (mostly women are affected by this factor).

Although reproductive effects of occupational exposure to hazardous chemicals have been well documented .

Endocrine-disrupting chemicals (EDC) are synthetic and naturally occurring chemicals that cannot be classified by any unique physical or chemical properties but are characterized by their ability to mimic the effects of endogenous hormones.

Specifically EDC can mimic and antogonize the action of endogenous hormones , induces the changes in steroid hormone level. These characteristics will leads to the harmful effect of human fertility.

Other cases such as, E. coli causes agglutination of human spermatozoa and thus, leading to infertility. This study evaluated if the negative influence of Escherichia coli on the motility of human spermatozoa is a consequence of E. coli adhesion.

Colony of Candida albicans can cause sperm clumping. 50% of the sperm in the specimen undergo clumping, thereby greatly reducing the effective sperm motile count.

Mycoplasma genitalium was demonstrated to adhere to all parts of the spermatozoa. Numerous M. genitalium cells bound to the spermatozoa were shown to cause sperm agglutination.

The Human Papillomavirus (HPV) is probably better known for its links with cervical cancer and other genital cancers also for its effects on male fertility.

Viral DNA from members of the Herpesviridae family, suchas herpes simplex virus (HSV) and , cytomegalovirus(CMV), Epstein-Barr virus (EBV), and human herpes virus(HHV) , has been detected in the semen of asymptomaticinfertile patients .

In particular,HSV-2 and CMV,which are sexually transmissible, have been extensively studied and can lead to fetal and neonatal abnormalities .

• Stress and Other Environmental Factors Affecting Fertility in Men and Women:Overview by Andres Negro-Vilar (Environmental Health Perspectives Supplements101 (Suppl. 2): 59-64 (1993)

• Environmental and occupational factors affecting fertility and IVF success by Edward V.Younglai1, Alison C.Holloway and Warren G.Foster (Human Reproduction Update, Vol.11, No.1 pp. 43–57, 2005 doi:10.1093/humupd/dmh055Advance Access publication December 15, 2004.)

• http://www.parents.com/getting-pregnant/infertility/causes/factors-affecting-fertility/.

• http://www.conceiveonline.com/articles/12-most-common-factors-affecting-female-and-male-fertility.

• http://scholarsresearchlibrary.com/aasr-vol3-iss5/AASR-2011-3-5-618-623.pdf.