Trichomoniasis, nicknamed "trick," is a sexually transmitted disease (STD) caused by a microscopic one-celled organism called Trichomonas vaginalis. Trichomoniasis can cause vaginal infections in women and inflammation of the urethra (the tube that drains urine from the bladder) in both sexes. In pregnant women, Trichomonas infections also can increase the risk of premature rupture of the membranes and preterm delivery.
Trichomonas is passed from an infected person to his or her partner during sexual intercourse without a condom. Currently, Trichomonas infections affect approximately 3 million women in the United States each year. Men can pass the infection on to their sexual partners, but they rarely develop symptoms themselves.