Menstruation: Facts, Statistics, and Information

A menstrual period is vaginal bleeding that occurs at the end of the menstrual cycle. Each month, the female body prepares itself for a possible pregnancy. The uterus develops a thicker lining, and the ovaries release an egg that can be fertilized by sperm.

If the egg isn’t fertilized, pregnancy won’t occur during that cycle. The body then sheds the built-up uterine lining. The result is a period, or menstruation.

The average female will have their first period between ages 11 and 14. Periods will continue regularly (usually monthly) until menopause, or about age 51.

Learn more about the facts and statistics of menstruation below.

Menstrual health and complications

The average menstrual cycle is 24 to 38 days. The typical period lasts four to eight days.

Monthly or regular periods are a sign your cycle is normal. Your body is working to prepare for a possible pregnancy.

In addition to bleeding, 90 percent of people who menstruate say they experience various symptoms. Food cravings are one common symptom. In fact, one studyTrusted Source found that almost half of American women crave chocolate at the start of their period.

Breast tenderness is another common period symptom. It can peak in the days just before menstruation starts. A surge in the hormones estrogen and progesterone leads to enlarged breast ducts and swollen milk glands. The result is soreness and swelling.

Meanwhile, period pain (also called dysmenorrhea, aka “cramps”) is another common symptom. More than half of menstruating people experience some pain around their period, with some estimates saying as much as 84 percentTrusted Source.  

Prostaglandins are the cause of this pain. These are chemicals that trigger muscle contractions in your uterus. These hormones help the body shed the excess uterine lining, which can cause pain and cramping in the first days of your period.

Some people don’t have regular periods. Intense exercise or certain medical conditions can lead to irregular periods. Irregular periods can also occur in people who are:

• obese
• breastfeeding
• perimenopausal
• stressed

Painful, irregular, or heavy periods affect up to 14 percent of females in their childbearing years, estimates WomensHealth.gov. Moreover, a 2012 study found 32 to 40 percentTrusted Source of people who have periods report this pain is so severe they have to miss work or school.

The most common period-related health conditions include the following:

Endometriosis

Endometriosis causes uterine tissue to grow outside the uterus. During your period, hormones make this misplaced tissue painful and inflamed. This can lead to severe pain, cramping, and heavy periods.

Endometriosis affects 1 in 10 women between the ages of 15 and 49, estimates the American College of Obstetricians and Gynecologists. They note 30 to 50 percent of people with the disorder will experience infertility.

Uterine fibroid

These noncancerous tumors develop between the layers of tissue in your uterus. Many females will develop at least one fibroid during their lifetime. In fact, by age 50, 70 percent of white women and 80 percent of African-American women will develop one.

Menorrhagia

Menorrhagia is very heavy menstrual bleeding. Typical periods produce 2 to 3 tablespoons of menstrual blood. People with menorrhagia can produce more than twice that amount. More than 10 millionTrusted Source American women have this condition, estimates the Centers for Disease Control and Prevention.

Premenstrual syndrome (PMS)

This is a series of symptoms that typically occur in the week or two before the start of a period. Symptoms can include:

• headache
• fatigue
• bloating
• irritability

PMS affects as many as 3 in 4 women, reports WomensHealth.gov.

Premenstrual dysphoric disorder (PMDD)

PMDD is similar to PMS, but is more severe. It can cause:

• depression
• tension
• severe mood shifts
• lasting anger or irritability

Experts estimate about 5 percent of women experience PMDD.

Poor menstrual hygiene

Poor menstrual hygiene is also a health concern during your period. Blood and tissue loss during a period can lead to bacterial issues. This can pose a serious health issue when or if menstrual products aren’t available or basic sanitation utilities aren’t accessible, such as clean water.

Menstruation throughout the ages

The stigma surrounding menstruation dates back centuries. References to menstruation are found in the Bible, Quran, and Pliny the Elder’s “Natural History.”

In these references, menstruation is referred to as “harm” and “unclean,” and a thing that can turn “new wine sour.”

Decades of faulty research did little to dispel the stigma that surrounds periods, too.

In 1920, Dr. Béla Schick coined the phrase “menotoxin” for a theory he had that women produce toxins during menstruation.

Schick reached this conclusion after a nurse who was menstruating handled a bouquet of flowers. Schick observed that those specific flowers wilted sooner than flowers the nurse didn’t touch. He decided her period was the cause.

In the 1950s, researchers injected menstrual blood in animals to test the toxic theory. The blood did, in fact, kill the animals. But it was proven years later that the death was a result of bacterial contamination in the blood, not a toxic effect.

By 1974, researchers had identified that menstruation taboos may be closely tied to how men participate in procreative activities. In other words, the less men are involved with childbirth and childrearing, the more distasteful a period is to them.

Period hygiene has also been an ever-evolving production.

In 1897, Lister’s Towels were introduced by Johnson & Johnson as the first mass-produced and disposable menstrual pad. These were far from the period pads of today. They were thick pads of material worn inside undergarments.

The Hoosier Ladies’ Sanitary Belt came a few decades after the turn of the century. The belt was a series of straps meant to hold reusable sanitary pads in place.

A few short years later, in 1929, Dr. Earle Haas invented the first tampon. His idea came from a friend who mentioned using a sea sponge tucked into her vagina as a way to absorb period blood.

The adhesive sticky pads used today weren’t introduced until the 1980s. Since then, they’ve been honed and updated to meet changing lifestyle, flow, and shape needs.

Today’s period products seek to solve many of the issues menstruating individuals have dealt with for decades, from leaks and period tracking to cost. They’re also helping remove the stigma that often surrounds menstruation. Plus, they seek to solve environmental and financial concerns.

These products include reusable menstrual cups and period underwear. There are also many smartphone apps that can help people better understand how their body prepares for, and acts during, their period.