An Overview of Menstruation

In This Article

From your first period (menarche) until your periods stop with menopause, the sole purpose of your monthly cycle is to reproduce. If a fertilized egg does not implant in the wall of your uterus after ovulation, the lining sheds. This is your menstrual period. Menstruation happens every month because you did not get pregnant.

A regular menses occurs, on average, every 28 days or about 14 days after regular ovulation. When the body does not function properly to cause ovulation, menstruation does not come regularly.

Believe it or not, the uterus is more of a bystander in this monthly process. The main players are two structures in the brain—the hypothalamus and the pituitary gland—along with the ovaries. Technically, this is referred to as the hypothalamic-pituitary-gonadal axis. When the interactions of this neuroendocrine trio function properly, ovulation and (if pregnancy doesn’t result from fertilization of the released egg) menstruation happen at regular intervals.

Menstrual Cycle Stages

A lot of hormonal changes happen in your body leading up to your period. These hormone changes happen in a predictable way every month and the change they cause in your body is called your menstrual cycle, which includes:

Day One

Menstruation is the cyclic shedding of the lining of the uterus so it seems like menstruation would mark the end of your menstrual cycle. Even the common term for menstruation—"your period"—makes you think about something ending. But actually, menstruation marks the first day of a new cycle.

When bleeding starts, the brain has already initiated the hormone changes to trigger a new cycle.

Count the first day of menstruation as cycle day one.

Follicular Phase

As your period begins and the built up lining from the previous cycle is shed, your brain produces hormones that stimulate the ovaries to release estrogen and prepare an egg for ovulation. This is called the follicular phase.

Under the influence of the rising estrogen levels, the lining of your uterus, or endometrium, begins to thicken or proliferate.


In response to another change in hormone levels from your brain, your ovary releases an egg (oocyte) and ovulation occurs. This usually happens on cycle day 14.

Luteal Phase

The follicle that released the egg now begins to shrink. It continues to produce estrogen but also begins to produce progesterone. It is called the corpus luteum.

Although both estrogen and progesterone are produced during this part of the cycle, progesterone concentrations dominate. Under the influence of progesterone, the lining of the uterus begins to change in ways to prepare it for pregnancy.

In the last half of the cycle, the now built up lining becomes thicker and more complex with glands, blood vessels, and tissue swelling. These are all changes that prepare the uterine lining for the process of implantation and pregnancy. If implantation of a fertilized egg does not occur, the corpus luteum in the ovary continues to shrink away.

During this time, estrogen and progesterone levels continue to fall. When this happens, the blood vessels that expanded in the thickened lining constrict and cut off blood flow. The thickened lining, now without blood flow to support it, dies and is shed from the uterus.

Menstruation Basics

A normal period is not an illness or a disability. There is no medical reason to limit physical activity during your period, including swimming, yoga, and all extreme sports. It is also completely safe, albeit messy, to have sex during menstruation.

Some women, however, have very heavy bleeding and/or very painful periods. This is not normal.

If you are not participating in your normal activities or if you are missing work/school because of painful or heavy periods, discuss it with your doctor.


There are many options to help you manage your menstrual flow. You may choose a feminine hygiene product based on convenience, comfort, or lifestyle. Whatever product you chose, it is important to change them frequently. You should consider avoiding products that contain fragrance or perfume as they can be very irritating.

Some women feel they need to clean out their vagina after their monthly menstruation by using a douche. Not only is this not necessary, but it also may be harmful. When you douche, you actually kill off the good bacteria in your vagina that keeps it clean and healthy.

Changes in Your Period

Obviously, your menstrual cycle is unique to you. How much you bleed, when you start, and for how long is unlike anyone else. But, it is also common and very normal for your own menstruation to change from month to month. A normal range for menstruation is every 21 to 35 days. 

Depending on the month, your period may come a few days early/late or your menstrual flow may be heavy/light. Many factors can influence the hormone changes in your body, including:

  • Stress
  • Exercise
  • Weight gain/loss
  • Travel
  • Illness

Some women's cycles are more sensitive to fluctuations in hormone levels than others. Although it is normal for menstruation to vary, it is also normal for it to stay completely regular.

Late or Missed Periods

Once you've started having regular periods, missing your monthly menstruation could be a sign of an underlying medical issue. If you are having sex, the most common cause of a missed period is pregnancy.

It is normal to miss a period occasionally. Consider taking a pregnancy test if you are more than seven days later or have missed a period.

If you are not pregnant, a missed period usually means that ovulation did not occur. The same things that can influence menstrual flow, like stress and exercise, can influence ovulation.

As long as you have determined that you are not pregnant, it is ok to wait another month to see if your period comes. If you miss your menstruation for two or three months in a row, you should talk to your doctor. 

A Word From Verywell

Menstruation is a normal function of a woman's body. You should not be ashamed about your period. And your period shouldn't interfere with your lifestyle. If you are having problem periods, you should talk to your doctor. Your menstruation is not a reason to stop living well.

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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Fleming R, Jenkins J. The source and implications of progesterone rise during the follicular phase of assisted reproduction cycles. Reprod Biomed Online. 2010;21(4):446-9. doi:10.1016/j.rbmo.2010.05.018

  2. Petersen JF, Andersen AN, Klein BM, Helmgaard L, Arce JC. Luteal phase progesterone and oestradiol after ovarian stimulation: relation to response and prediction of pregnancy. Reprod Biomed Online. 2018;36(4):427-434. doi:10.1016/j.rbmo.2017.12.019

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