Pelvic fluid does not affect menstruation. Pelvic fluid is mainly seen in two situations: 1) physiological fluid; physiological fluid is related to monthly follicle rupture; 2) pathological fluid: pathological fluid is related to chronic pelvic inflammation. Menstruation is related to the function of the hypothalamic-pituitary-ovarian axis, so pelvic effusion has nothing to do with menstruation. Menstruation refers to the cyclic shedding and bleeding of the endometrium that accompanies the cyclic changes of the ovaries. Menstruation is cyclic and self-limiting, with an average of twenty-eight days in the menstrual cycle, and the menstrual period generally ranging from two to eight days, with an average of four to six days, with the first menstruation mostly occurring at the age of thirteen to fourteen years old, and regular menstruation is an important sign of the maturity of the reproductive function.