Trichomoniasis It is an infection of the genitals that is spread by sexual contact. It is one of the most common sexually transmitted diseases (STIs) or sexually transmitted diseases (STDs). It affects both sexes. But most are women ages 16 to 35. In the United States, about 2 million women are infected each year. The infection is not life-threatening. But it may lead to complications such as infertility. Infections of the skin tissue in the vagina (cellulitis) and, in men, blockage of the urethra. Infection during pregnancy can lead to premature delivery and low birth weight.