The menstrual phase is the first stage of the menstrual cycle, lasting about 3 to 7 days. During this phase, the lining of the uterus, which thickened in preparation for a potential pregnancy, sheds if fertilization does not occur. This process results in menstrual bleeding, which is a natural part of female reproductive health. Hormonal changes, particularly in levels of estrogen and progesterone, trigger the menstrual phase. Women may experience various symptoms, including cramps, mood swings, and fatigue. Understanding this phase is essential for recognizing the overall menstrual cycle and maintaining reproductive health.