Before we talk about irregular cycles, we need to first discuss what is considered regular. A regular menstrual cycle is defined as lasting from 24 to 38 days, from the first day of one period to the first day of the next period, with actual menstrual bleeding lasting up to 8 days (American College of Obstetricians and Gynecologists). Longer cycles are more common when menstruation first begins at puberty, but as the body ages, the menstruation cycle usually shortens (Mayo Clinic 2016).
That in mind, according to the Amercian College of Obstetricians and Gynecologists (ACOG), a cycle is considered irregular if it is shorter than 24 days, longer than 38 days (American College of Obstetricians and Gynecologists), or if the length varies from cycle to cycle (Santos-Longhurst 2018). Small differences are expected, and one or two extra long cycles among years of regular cycles are not necessarily a sign that something is amiss. For example, one of the most common causes of occasionally having a long cycle is stress, which delays ovulation by suppressing the hormones that cause ovulation, resulting in a longer cycle and the appearance of a late period (Weschler 2015) But if cycle lengths are often different from each other by more than 7-9 days, this may be an indication of an underlying issue (American College of Obstetricians and Gynecologists).
Another sign to monitor is your period itself. A normal period would generally follow the pattern of starting light, then getting heavy, and then becoming light again, or starting heavy and then becoming lighter as the days progress. Abnormal bleeding does not follow the usual pattern that a period would, is usually light brown or even black (Weschler 2018), and might be characterized by any of the following (American College of Obstetricians and Gynecologists):
Bleeding or spotting between periods
Bleeding or spotting after sex
Heavy bleeding during your period
Bleeding after menopause
Missing 3 or more periods in a row (negative pregnancy test)
Abnormal bleeding could be caused an underlying medical condition, so reporting these symptoms to your medical care provider is important for your fertility and overall health. Abnormal bleeding could be related to irregular cycles, which are caused by a variety of factors, from taking certain medications to health conditions like endometriosis. Common causes of irregular cycles include (WebMD 2017):
Changes to estrogen and progesterone
Birth control (17% of women in childbearing age are on the pill, according to the CDC)
Too much exercise
Pregnancy or breastfeeding
The following medical conditions can also cause irregular cycles and abnormal bleeding (WebMD 2017) with the percentage affected in childbearing age:
In other words, out of 10 women of childbearing age, an estimated one would have PCOS, one would have endometriosis, almost two would be on the pill, and up to two would have uterine fibroids. Not taking into consideration the many other factors that can cause irregular cycles, about half of our group of 10 will have a menstrual cycle that is considered irregular.
When discussing irregular cycles with health care providers, you may be provided several options. Some medical healthcare experts are wary of women with irregular cycles being prescribed hormonal contraceptives to treat this condition because, in some circumstances, this may only treat symptoms and not the underlying cause (Weschler 2018). However, oral contraceptives may have other added benefits secondary to preventing pregnancy. Taking oral contraceptives can clear up acne and can help to reduce heavy bleeding (menorrhagia) and severe pain (dysmenorrhea) during menstruation, which is precisely why they are often prescribed for PCOS and endometriosis (The ESHRE Capri Workshop Group 2005).
Some healthcare professionals may explore underlying conditions or recommend lifestyle changes -- like diet, exercise, and quitting smoking -- before drug therapy to ensure that other factors are not causing the symptoms. Toni Weschler, MPH, fertility expert and author of Taking Charge of Your Fertility, encourages charting symptoms to help identify patterns in your own cycle and to provide evidence that supports requests made to doctors for additional testing and diagnostics (Weschler 2018). In terms of healthcare particularly, knowledge is power.
While many sources still say that a typical menstrual cycle “should be” 28 days long, and this is the timeline that a cycle on hormonal birth control will follow, many other experts disagree. In fact, Cheryl Deets, MD says that 80% of cycles will be anywhere from 21 to 45 days long (Deets 2016). Variation in menstrual cycles can even be seen based on lifestyle, and deviating from that 28-day cycle is not actually a bad thing, states Assistant Professor of Anthropology at the University of Illinois, Urbana-Champaign Kate Clancy. “...This variation is adaptive, that when we vary from this false norm – really an extreme that does not reflect the physiology of most women of the world – and can identify lifestyle or environmental factors producing this variation, that it means our bodies are working properly” (Clancy 2010).
So how common are irregular periods? More common than we think! Adolescents don’t have a regular cycle, and neither do those in or beginning menopause. Someone with PCOS, endometriosis, or is breastfeeding, pregnant, or undergoing various hormone treatments probably wouldn’t have a regular period, and neither do many others. In reality, the menstrual cycle is more diverse than we give it credit for. On the other hand, irregular periods can be an essential body sign that something isn’t working right and can be a maker of chronic disease. Check out our blog, I Saw the 5th Vital Sign to learn more.