The Menstrual Cycle

Overview

Most people are first introduced to the menstrual cycle when they get their first period. However, the menstrual cycle is a much larger phenomenon than just bleeding each month.

Overall, the menstrual cycle refers to the hormonal fluctuations and associated physical symptoms that occur in the female body on a roughly month-long schedule starting at puberty. Hormones are small chemical “messengers” that travel throughout the body and trigger particular changes. The two hormones most associated with the menstrual cycle are estrogen and progesterone.

The primary purpose of the menstrual cycle is to prepare the body for pregnancy. However, the menstrual cycle occurs even when a woman is not trying to get pregnant or is not sexually active. Furthermore, the effects of the menstrual cycle are not limited to fertility-related symptoms.

Phases of the Menstrual Cycle

The menstrual cycle typically lasts between 21-35 days and consists of four main phases:

• Menses Phase

• Follicular Phase

• Ovulatory Phase

• Luteal Phase

Each phase is described in further detail below.

Menses Phase

The menstrual cycle starts with the menses phase, also known as a period. Bleeding during the menses phase is caused by the shedding of the walls of the uterus (known as uterine lining). During the rest of the menstrual cycle, the uterine lining Is thickened to prepare for the possibility of supporting a baby during pregnancy. However, if a woman does not become pregnant, the thick uterine lining is not needed and is expelled from the body. Women only have a menses phase when they are not pregnant.

The menses phase typically lasts 3-7 days and should include at least one day of medium or heavy bleeding.

Estrogen and progesterone levels are both lowest during the menstrual phase.

Follicular Phase

The follicular phase also begins on the day that bleeding starts but continues until about day 14 of the cycle. During the follicular phase, both estrogen and progesterone levels start to rise, and the lining of the uterus begins to thicken again after the menses phase ends.

Other hormones are also active during the follicular phase and cause a mature egg to develop in the ovaries.

Ovulatory Phase

The ovulatory phase or ovulation occurs when the mature egg is released from the ovaries.

Ovulation occurs around day 14 and is the point in the menstrual cycle when estrogen is highest.

A woman is most likely to get pregnant if she has sex in the days surrounding ovulation.

Luteal Phase

The luteal phase begins after ovulation and lasts until the first day of the menses phase. Progesterone levels are highest during the luteal phase, and the uterine lining continues to thicken.

During the luteal phase, the egg moves through the fallopian tubes from the ovaries to the uterus. If the egg is fertilized during this time and attaches to the wall of the uterus, the woman will become pregnant. Otherwise, the uterine lining begins to shed, and the egg is expelled during the menses phase.

The menstrual cycle and associated changes in basal body temperature, hormones, and ovarian and uterine structure. Source: By Isometrik, Kaldari; Begoon; Marnanel - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=148851325

Other Symptoms

Due to the hormonal fluctuations and physical changes described above, the menstrual cycle affects other aspects of life, including energy levels, mood, and social behavior. Women may feel differently during different phases of the cycle and can expect basic patterns to repeat from month to month.

Other physical symptoms also occur, such as cramps or back pain during the menses phase or thick and slippery cervical mucus during ovulation (this may be noticeable in a woman’s underwear or when she wipes).

Symptoms vary from person to person, however, and not everyone will experience the menstrual cycle in exactly the same way.

Summary

Although the period is the most obvious symptom of the menstrual cycle, there is a lot more going on in the body over the entire month. Being aware of these fluctuations and symptoms allows for greater alignment with the body and better understanding of what to expect on any given day.