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Menstrual Cycle: Introduction

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Cycle Overview
The average length of the menstrual cycle is 28 days.

The menstrual cycle is a naturally occurring function in women of reproductive age. The average length of the cycle is 28 days and is comprised of four phases: menstruation, the follicular phase, ovulation, and the luteal phase.

During the menstrual cycle, your body undergoes many physiological and hormonal changes. The process begins with your brain triggering certain hormones to stimulate egg growth. Once the egg matures it will release from the ovary and travel through the fallopian tube into the uterus. If the egg is not fertilized by sperm, it will disintegrate and be absorbed. When the egg goes unfertilized, hormone levels will drop causing the lining of the uterus to shed and bleed resulting in a discharge through the vagina. Bleeding (also known as your menstruation or your “period”) generally lasts around five days, but that varies from woman to woman.

Do You Know?
  • Irregular periods may occur in some women. Some factors that might cause an abnormal period includes the use of birth control pills, low or high body fat, weight gain or loss, stress, extreme exercise, and pregnancy.
  • The menstrual cycle has a limited life span. It begins around 11 to 14 years of age (or at the onset of puberty) and lasts until around 50 (or at the onset of menopause).
  • The duration of the menstrual cycle can vary. It can last from 24 to 42 days when counting from the first day of bleeding in one cycle to the first day of bleeding in the next cycle.