Causes of infertility include a wide range of physical, as well as emotional factors. Approximately 30 to 40% of all infertility is due to a "male" factor (such as retrograde ejaculation, importance, hormone deficiency, environmental pollutants, scarring from sexually-transmitted disease, or decreased sperm count due to heavy marijuana use or prescription drugs such as cimetidine, spironolactone, and nitrofurantoin).
A "female" factor (for example, scarring from sexually-transmitted disease, ovulation dysfunction, poor nutrition, hormone imbalance, cysts or cancer of the ovaries or uterus, pelvic infection or tumor, or transport system abnormality from the cervix through the Fallopian tubes) is responsible for 40 to 50% of infertility in couples. It is estimated that 10 to 20% of couples will be unable to conceive after one year of attempting to become pregnant. It is important that pregnancy be attempted for an extended period (at least one year); the chances for pregnancy occurring in young healthy couples, having intercourse regularly, is only 25 to 30% per month.
Increased risk for infertility is associated with: having multiple sexual partners (therefore increasing the risk for STDs), having a sexually-transmitted disease, having a past history of PID (pelvic inflammatory disease) (after single episode 23% of women become infertile), having a past history of orchitis or epididymitis in men, having mumps orchitis (men), having a past medical history inclusive of DES exposure (men or women), having eating disorders (women), having anovulatory menstrual cycles, having a chronic disease (such as diabetes)
Because infertility is frequency caused by sexually-transmitted diseases, practicing safer sex behaviours may minimize the risk of future infertility. Gonorrhea and chlamydia are the two most frequent causes of STD-related infertility. These diseases are often initially asymptomatic until PID or salpingitis develops. These inflammatory processes cause scarring of the Fallopian tubes and subsequent decreased fertility, absolute infertility or and increased incidence of ectopic pregnancy.