It is normal for menstruation to be a week early, but if it is 10 days early, it is not normal. Under normal circumstances, women’s menstruation is affected by their living environment and work pressure, and it is normal to have a week early or a week late, because the level of hormones secreted by the ovaries also changes dynamically and is easily affected by external negative influences. In a menstrual cycle, when the ovaries start to secrete estrogen after the menstruation, the endometrium grows and thickens, and during ovulation the endometrium grows to a thicker range, around 0.9cm, while in the late ovulation period it is influenced by progesterone to thicken even more. Before the onset of menstruation, estrogen and progesterone drop together, causing the endometrium to lose its support, which leads to the onset of menstruation.