Vaginal discharge is one of the most common reasons for gynecological visits in the US, accounting for about 10 million office visits per year. 
Physiologic vaginal discharge
Normal vaginal discharge in a reproductive-aged woman, also called physiological leukorrhea, usually consists of 1 to 4 mL per 24 hours. It is typically transparent, mucousy, and white-to-yellowish. It is typically odorless but can also be slightly malodorous. The character of physiological discharge can vary over time. For instance, it becomes more noticeable with higher estrogen states (e.g., pregnancy, use of estrogen-progestin contraceptives, or at ovulation). Lactobacilli in the normal vaginal flora maintain normal acidity in vaginal discharge by producing hydrogen peroxide and lactic acid. The normal pH of leukorrhea in reproductive women (4.0 to 4.5) creates a hostile environment for pathogens to grow. In premenarchal and postmenopausal women with low estrogen states, vaginal pH may be 4.7 or more.
The true prevalence of this condition is uncertain because vaginitis, which encompasses the symptom vaginal discharge, is often asymptomatic, self-diagnosed, and self-treated. A telephone survey revealed that 8% of white women and 18% of black women had at least 1 episode of vaginal symptoms in the previous year.