Having a period 10 days early is not pregnancy, because having a period means that you are not pregnant and is often considered to be an irregular menstruation. The occurrence of menstruation in women is related to the level of hormones in the body. During the menstrual cycle, a woman will have an ovum that is expelled waiting to be fertilized and the endometrium will proliferate. Once the expelled egg is not fertilized, the unexpelled egg will degenerate into the corpus luteum, which secretes progesterone. If the egg is not fertilized, the corpus luteum begins to shrink 9-10 days after ovulation, luteinizing hormone secretion decreases, and the endometrium is unable to sustain itself due to insufficient hormonal support and thus shedding occurs, resulting in the onset of menstruation. Thus the appearance of menstruation marks the absence of pregnancy. In conclusion, the onset of menstruation 10 days early is often considered to be irregular. Patients are advised to take rest during this period, not to exercise strenuously, and to take nutritional supplements to ensure a smooth passage through this special period, and if it continues to occur they should seek medical attention to check the cause for treatment.