Some factors can affect how easily a woman ovulates, gets pregnant, or delivers a child. These include:

• Age. Women in their late 30s and older are generally less fertile than women in their early 20s.

• Endometriosis

• Chronic diseases such as diabetes, lupus, arthritis, hypertension, and asthma

• Hormone imbalance

• Environmental factors. These include cigarette smoking, drinking alcohol, and exposure to workplace hazards or toxins.

• Too much body fat or very low body fat

• Abnormal Pap smears that have been treated with cryosurgery or cone biopsy

• DES taken by mother during pregnancy

• Sexually transmitted diseases

• Fallopian tube disease

• Multiple miscarriages

• Fibroids

• Pelvic surgery

• Abnormalities in the uterus that are present at birth or happen later in life

Infertility is not just a woman's problem. Here is a list of things that can affect a man's fertility:

• History of prostatitis, genital infection, or sexually transmitted diseases

• Exposure to hazards on the job or to toxic substances. These include radiation, radioactivity, welding, and many chemicals. Toxic chemicals include lead, ethylene dibromine, and vinyl chloride.

• Cigarette or marijuana smoke

• Heavy alcohol drinking

• Exposure of the genitals to high temperatures

• Hernia repair

• Undescended testicles

• Prescription medicine. These include opioid-like medicines that affect the central nervous system. An example is medicines to treat mental illness.  

• Mumps after puberty 

• A genetic problem or a problem that was present at birth (congenital)