Toxic effects related to tobacco, marijuana, and other drugs
Smoking may cause infertility in both men and women. In experimental animals, nicotine has been shown to block the production of sperm and decrease the size of male testicles. In women, tobacco changes the cervical mucus, thus affecting the way sperm reach the egg.
Marijuana may disrupt a woman's ovulation cycle, affecting the release of the egg. In men, marijuana use can decrease the sperm count as well as affect the quality of the sperm.
In women, the effects of alcohol are related to severe consequences for the fetus. And chronic alcoholism is related to disorders in ovulation, which interferes with fertility. Alcohol use by men interferes with the synthesis of testosterone and has an impact on sperm concentration. Alcoholism may delay a man's sexual response and cause impotence by interfering with a man's ability to have an erection.