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Irregular periods explained: 8 big reasons your period's gone MIA

Sarah Kelsey is a lifestyle writer, editor and spokesperson based in Toronto. She was the editor of AOL/The Huffington Post Canada’s StyleList, Style and Living sites. Today, she's a freelancer writing for some of North America’s top pub...

Everything you ever wanted to know about irregular periods — it doesn't always mean you're pregnant

A monthly cycle has been called "the curse," but that doesn't mean you don't miss it when it's gone. Having the predictability of a monthly period can mean a lot of things. Firstly, you're not pregnant, and three cheers for that. And secondly, a regular cycle can also signify that your reproductive health is in working order. Frustrating doesn't even begin to describe what it's like to deal with a period that does whatever it damn well pleases — showing up early, late or sometimes not at all.

Because a woman's body and hormonal system can be so sensitive, irregular periods are fairly common, though that doesn't make them any easier to deal with. Barring any potential medical issues, you can give yourself some peace of mind by trying to find the underlying trigger that could be keeping your period at bay:

A normal period versus an irregular period

"The monthly menstrual cycle typically occurs every 28 days, is controlled by various hormones and is a key function of the female body," says Dr. Sherry Ross, MD, OB/GYN and Women’s Health Expert at Providence Saint John’s Health Center in Santa Monica, California. "Your 'period' begins around 11-12 years of age, lasts 2-7 days and continues until your reach menopause, which occurs around 51 years old."

Dr. Ross continues, "Ovulation is an important part of the menstrual cycle and occurs around Day 14 when an ovarian follicle produces an egg, which can be fertilized by sperm. The egg is only available to be fertilized for 24 hours before it disintegrates. Once you have ovulated, your period will occur, which is typically 14 days later."

The amount of blood shed during a period varies from woman to woman. Some women routinely have heavier periods (losing up to 12 teaspoons of blood each month) while others may experience a period that's almost non-existent (losing as little as four teaspoons of blood).

More: The Mamafesto: Menstruation shaming has to end. Period.

If you've been menstruating for a while, your body will get into a period flow, which is why an irregular period is usually defined as any type of bleeding that's abnormal when compared to your last few menstrual cycles. It can include everything from a late period to early bleeding, and scant bleeding to extremely heaving bleeding. For many women, this can even mean an absent period (amenorrhea) or two periods in one month (metrorrhagia). Two periods in one month, or a period every two weeks, are thought to be caused by an imbalance in estrogen and progesterone and may require a trip to the doctor since this can induce anemia.

And if you're not prone to PMS, you can also consider a period irregular if you experience heavy cramping and bloating or headaches.

The many causes of irregular periods

Every woman will experience an irregular period from time-to-time, and though, in most cases, they aren't dangerous, it's important to figure out what's causing the irregularity. Here are a few common reasons you may be experiencing an abnormal flow.

1. Stress

Everything you ever wanted to know about irregular periods — it doesn't always mean you're pregnant
Image: Film Magic/Film Magic/Getty

Stress is the most common cause of irregular periods. Cortisol, the stress hormone, has a direct impact on how much estrogen and progesterone, two sex hormones, gets produced by the body. If you have too much cortisol in your bloodstream, the time and flow of your cycle could change. Dr. Carolyn C. Thompson, MD, FACOG, board-certified OB/GYN, says, "In order for a woman to have a normal menstrual cycle (in which she does not become pregnant), the hypothalamus in the brain must send hormonal signals to the pituitary gland, which must in turn signal the ovary, which then signals the uterus. The hypothalamus is adjacent to areas in the brain that influence emotion; neurotransmitters form these centers can shut down the signals to the hypothalamus and therefore stop the outgoing signals from the hypothalamus. Evolutionarily speaking, this makes sense — if a woman is under a great deal of stress, either physical or emotional, it is likely not an ideal time for a pregnancy, so the system shuts down."

More: Stress or PMS: What is making you moody?

2. Diet

Everything you ever wanted to know about irregular periods — it doesn't always mean you're pregnant
Image: Digital Vision/Getty Images

Another common reason for a late or missing period is the food you eat and, more specifically, the weight you're carrying. If you're eating a diet that's rich in unhealthy carbs or if you've gained weight, your body will produce varying levels of certain hormones, shifting when you ovulate. The same goes for women as they lose weight. "In order for a woman to maintain a regular cycle, her body fat percentage needs to be at least 17-22 percent. This is again related to the evolutionary idea that a state of starvation is not conducive to maintaining a healthy pregnancy, so, again, the system shuts down," says Dr. Thompson.

3. Exercise

Everything you ever wanted to know about irregular periods — it doesn't always mean you're pregnant
Image: John Fedele/Blend Images/Getty

Our bodies need energy to menstruate. If you're burning too much of your energy in the gym, there will be nothing left for your body to use during that time of the month. "The list of what causes irregular periods is longer than you think, but we know excessive exercising, sudden weight changes and being underweight can offset your hormone levels. One of these hormones is called Leptin and is produced in fatty tissue. Excessive exercising and drastic weight changes can decrease the body fat, causing this and other hormones to drop, contributing to irregular periods," says Dr. Ross.

4. Birth control pills

Everything you ever wanted to know about irregular periods — it doesn't always mean you're pregnant
Image: Jamie Grill/Getty Images

It can take several months for your body to get used to the dose of hormones birth control pills deliver. On top of that, Dr. Ross explains, "One of the side effects of a low dose birth control pill is a light or non-existent period. For many, this is a welcomed side effect! When some women stop taking the pill, their periods may take one to three months to return to normal. The birth control pill doesn’t cause you to have amenorrhea. It may be once you are off the pill you may find you have an underlying hormonal problem that was masked by taking the birth control pill. If this is the case, you should alert your healthcare provider."

Next Up: Polycystic ovary syndrome (PCOS)

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