The term “period” generally refers to a woman’s menstruation. The first menstruation may be preceded by the growth of pubic and armpit hair, increased vaginal discharge, and a vague pain in the lower abdomen, but it is not absolute, after all, every woman’s physical condition is different. 1. Growth of pubic hair and armpit hair: Women may experience growth of pubic hair and armpit hair before menstruation due to the gradual development of ovarian function and increased secretion of adrenal androgens. 2. Increase in vaginal secretion: the endocrine environment of the body changes before the onset of menstruation, and the increase in estrogen stimulates the cervix, endometrial glands and vaginal glands to increase secretion, which mixes together to form leucorrhoea, that is, the vaginal secretion increases, showing milky-white or transparent leucorrhoea. 3. Hidden pain in the lower abdomen: the pelvis will be congested before the onset of menstruation, and there may be hidden pain in the lower abdomen after the congestion. As there are differences between individuals, the precursors of menstruation may also be different, and it is recommended to consult a medical professional for details.