What day of the menstrual cycle does a woman have her period?

A period, also known as menstruation, generally occurs during the first few days of the menstrual cycle. The menstrual cycle is a monthly cycle that involves the shedding of the lining of the uterus (womb) in preparation for a possible pregnancy. It is counted from the first day of menstrual bleeding to the day before the next period starts.

On average, a menstrual cycle lasts about 28 days. However, it can vary from 21 to 40 days or even longer in some women. Menstruation typically lasts for 3-7 days, but this can also vary.

The period of menstrual bleeding is the last phase of the menstrual cycle, which is known as the menstrual phase or the luteal phase. During this phase, the levels of the hormones estrogen and progesterone, which were produced in the previous phases to thicken the uterine lining in preparation for pregnancy, decline. This causes the shedding of the uterine lining through the vagina, resulting in menstrual bleeding.

The start of menstrual bleeding marks the beginning of a new menstrual cycle.