What is a menstrual period or just period?

Every month, your body prepares for pregnancy by ovulating, ejecting an egg from the ovary. If pregnancy does not happen, then a menstrual period begins usually 12-16 days after ovulation. The menstrual blood is partly blood and partly tissue from inside the uterus. It passes out of the body through the vagina.

Menstruation or menstrual period is the normal regular shedding or vaginal bleeding of the uterine lining each month or so. In response to ovulation, the uterine lining starts building up and if no pregnancy occurs, the uterus, or womb, sheds its lining. That bleeding in response to ovulation and no pregnancy happening is called a period.

When a person with a uterus and ovaries menstruates, has a menstrual period, the body discards the monthly buildup of the lining of the womb (uterus). Menstrual blood and tissue flow from the uterus through the small opening of the cervix at the bottom of the uterus and then passes through the vagina out of the body. Menstruation, or a menstrual period, occurs as part of a person with ovaries and uterus'  monthly menstrual cycle which is associated with regular ovulation, the ejection of an egg from the ovary. A person with a uterus and ovaries usually starts the menstrual period if pregnancy did not happen. The menstrual period usually starts about 14 days (range 12-16 days) after ovulation if there is no pregnancy. The menstrual period (as well as your menstrual cycle) begins on the first day you see bright red blood.

If there is a pregnancy, then a woman does not get her period.

Your menstrual cycles are a window into your health. They are considered your fifth vital sign as they may indicate other medical issues now or in the future.

What is the menstrual cycle?

Your menstrual cycle begins on the first day of your menstrual period, the first day you see blood, and it ends on the day before the next period begins. A normal menstrual period is between 3-7 days long, and a normal menstrual cycle is between 21 and 35 days long with an average of 28 days.

Why it's important to know more about your menstrual cycles

Your menstrual cycles are a window into your health. They are considered your fifth vital sign as they may indicate other medical issues now or in the future. Menstrual cycle abnormalities, changes in cycles that have a difference of more than 3-4 days,  are often related to ovulation issues. With menstrual cycle anomalies, a person either does not ovulate or ovulation was earlier or later.

Not every vaginal bleeding is a period

Many times, vaginal bleeding is misinterpreted as a period. Every period is associated with vaginal bleeding but not every vaginal bleeding is a menstrual period.

What is an irregular menstrual period or cycle?

To define an irregular period or cycle, you first need to know what exactly a regular period and cycle is:

• A regular cycle happens every 24-32 days, with only 2-3 days difference each month
• A cycle that lasts less than 21 days is too short
• A cycle that lasts over 35 days is too long
• A regular period is a period with normal bleeding, not too much and not too little, and not for too many days.
• A period that lasts less than 2 days is too short or if it lasts over 5-6 days it is too long
• A period where you do not need any pads or tampons is not enough bleeding
• A period requiring frequent tampon changes or where blood soaks the pad quickly or with large clots is too much

Irregular menstrual cycles and women's health

Studies have shown that irregular menstrual cycles are not just an impediment to fertility but irregular and long menstrual cycles in adolescence and adulthood are associated with a greater risk of premature mortality (age <70 years).  Your menstrual cycles are your fifth vital sign. Irregular and long menstrual cycles have been associated with a greater risk of:

• coronary heart disease
• cancer
• mental health problems, and
• multiple other common chronic conditions.

For example, one cause of irregular cycles, PCOS, a common endocrinologic disorder found in many women, has also been associated with a higher risk of type 2 diabetes, dyslipidemia, non-alcoholic fatty liver disease, coagulation disorders, and possibly cardiovascular disease. These data collectively indicate that menstrual cycle dysfunction might accelerate the risk of premature mortality.

Terminology of abnormal menstrual bleeding

Doctors use certain words to describe abnormalities of the menstrual periods/bleeding and menstrual cycles:

Eumenorrhea - Normal periods: 

Eumenorrhea is defined as a normal menstrual period, normal menstrual bleeding that has no abnormalities of flow, timing, or pain. It is regular, not too heavy or too light.

Hypomenorrhea - Too light periods

Hypomenorrhea is when you have regular menstrual cycles but your period or bleeding is light and short. You may not need a tampon because the bleeding is so light and/or the bleeding lasts only a day or so. Hormone pills, IUDs with hormones, or birth control pills could normally make your periods lighter or could make them go away altogether. Being pregnant can also make your period go away altogether or appear lighter.

Hypomenorrhea, a light but regular menstrual period, in and of itself is unlikely to be a problem as long as you are ovulating regularly. However there are certain medical conditions, such as 'Asherman-Syndrome,' those are scars inside the uterus, which can lead to light and short menstrual periods. If you are trying to get pregnant and having problems conceiving, you may want to see an infertility specialist (RE=Reproductive Endocrinologist) to discuss your hypomenorrhea.

Amenorrhea - No periods

Amenorrhea is defined as having no menstrual period, no menstrual bleeding, or missed periods. There are one or more missed menstrual periods, sometimes even missing at least three menstrual periods in a row. Girls who haven't begun menstruation by age 16 are considered to have primary amenorrhea.  The most common cause of amenorrhea is not ovulating including pregnancy and menopause. Other causes of amenorrhea/anovulation include PCOS, polycystic ovary syndrome, thyroid disease such as hypothyroidism, certain medications, too high or too low weights, too much exercise, premature menopause, uterine abnormalities like scarring inside the uterus (Asherman syndrome).

Primary amenorrhea

Primary amenorrhea is when a person with ovaries and uterus has not yet had a menstrual period by the age of 16 years.

Secondary amenorrhea

Secondary amenorrhea is when the menstrual period stops regular menstrual cycles and periods (two of the most frequent diagnoses for 'secondary amenorrhea' are pregnancy and menopause). Anovulation such as pregnancy and menopause are among the main reasons for secondary amenorrhea. 

Menorrhagia - Heavy bleeding 

Menorrhagia is heavy menstrual bleeding during a menstrual period or prolonged menstrual bleeding (more than 5-6 days)

Metrorrhagia - Irregular bleeding

Metrorrhagia is an irregular timing of the menstrual periods (usually more frequent periods). It may also be bleeding in between otherwise regular periods.

Menometrorrhagia

Menometrorrhagia is irregular and frequent periods that are particularly heavy.

Oligomenorrhea - Infrequent periods

Oligomenorrhea is when periods happen less than 8 times a year or cycles coming less frequently than every 35 days. Oligomenorrhea is when cycles last over 35 days on average. Oligomenorrhea, similar to other period anomalies, is due to ovulation problems such as PCOS or premature ovarian aging or failure.

Dysmenorrhea - Painful periods

Dysmenorrhea is painful menstrual periods. A medical condition that involves pain or discomfort during the menstruation process, often simply referred to as menstrual pain. One main reason for the painful menstrual period is a condition called endometriosis.

Sources:

• Wang YX et al. Menstrual cycle regularity and length across the reproductive lifespan and risk of premature mortality: prospective cohort study. as: BMJ 2020;371:m3464
• Cirillo PM, Wang ET, Cedars MI, Chen LM, Cohn BA. Irregular menses predicts ovarian cancer: Prospective evidence from the Child Health and Development Studies. Int J Cancer 2016;139:1009-17. doi:10.1002/ijc.30144
• Solomon CG, Hu FB, Dunaif A, et al. Menstrual cycle irregularity and risk for future cardiovascular disease. J Clin Endocrinol Metab 2002;87:2013-7. doi:10.1210/jcem.87.5.8471
• Solomon CG, Hu FB, Dunaif A, et al. Long or highly irregular menstrual cycles as a marker for risk of type 2 diabetes mellitus. JAMA 2001;286:2421-6. doi:10.1001/jama.286.19.2421