The Menstrual Cycle Explained

The purpose of each 28-day menstrual cycle is to get you physically ready for a potential pregnancy. Your body goes through massive changes that might affect you in different ways. Every woman’s body is different and her cycle unique. Therefore, it’s important to know yours so you can detect anything that could be out of the ordinary as well as plan your day-to-day life.

The Four Phases of the Menstrual Cycle

The menstrual cycle has four phases. Out of the four, we’re probably most familiar with the menstrual phase, when the bleeding occurs. We usually don’t tend to think so much about the other three phases—the follicular phase, ovulation, and the luteal phase.  All four, however, depend on the function of different glands and the hormones these glands produce, such as progesterone, oestrogen and the luteinizing hormone.

1. Menstrual cycle (approx. day 1 to day 5 of the cycle): The first day of your period is the first day of your cycle. If the egg cell doesn’t get fertilized, levels of oestrogen and progesterone drop. The preparations that were made inside your body to support an embryo, are no longer needed. The thickened lining of your uterus sheds and flows out of the vagina together with blood and mucus.

A woman’s menstrual phase, also referred to as menses, can last between 3 and 7 days. The cramps that often accompany this phase are caused by the contraction of the uterine and stomach muscles. Although uncomfortable, they help the fluid exit your body.

2. Follicular phase (approx. day 1 to day 13 of the cycle): This phase also starts on the first day of your menstruation and lasts until you ovulate. In this phase, your pituitary gland (a pea-sized gland located just behind the bridge of your nose) releases follicle-stimulating hormone or FSH.  This stimulates your ovaries to produce tiny sacs, called follicles, that contain immature egg cells. Usually, only one of the eggs matures. The process sets the body in motion. The uterus starts to prepare by developing a thicker lining that could serve as a perfect, nutrient-rich environment for an embryo.

3. Ovulation phase (mid-cycle, approx. day 14 of the cycle): This phase is marked by the release of a mature egg from the ovaries. The process is triggered by the luteinizing hormone, another hormone produced by the pituitary gland. The egg travels to the uterus via the fallopian tube where it waits for 24 hours to be fertilized. This is the time in your cycle when you can get pregnant. 

4. Luteal phase (approx. day 15 to day 28 of the cycle): The follicle that released the mature egg gradually changes into the corpus luteum; a tiny structure that produces progesterone and some oestrogen. The surge in hormone levels keeps the lining of the uterus thick and ready for a fertilized egg. If you don’t get pregnant, corpus luteum slowly shrinks away and the levels of sex hormones decrease again. This brings us to the start of the next cycle.

Each phase has its own characteristics and potential challenges. For example, during the luteal phase, some women may experience premenstrual syndrome (PMS).