Sexually transmitted diseases (STDs) are infections spread from one person to another during sexual relations. Chlamydia trachomatis (chlamydia) and Neisseria gonorrhoeae (gonorrhea) are bacteria that are common causes of STDs in the United States. Both infections can cause symptoms such as discharge from the vagina or penis, pain with urination, or abdominal pain. However, many people with chlamydia or gonorrhea have no symptoms. Treatment with antibiotic drugs is important to get rid of symptoms, avoid spreading the infection to other people, and prevent complications of the infections. In women, chlamydia and gonorrhea infection can cause difficulties in becoming pregnant (infertility). Infections in pregnant women can lead to premature or low-birthweight infants and serious infections in newborns.