What is the 28 Day Cycle Myth?

Have you been told that the menstrual cycle lasts 28 days? Or that ovulation happens on cycle day 14? Well, that’s a myth! Not every woman is the same or will experience the same menstrual cycle or phase lengths.

Before we move into why this common myth is so problematic, let’s review what the menstrual cycle actually is…

Marochkina Anastasiia / Shutterstock

There are three phases of the menstrual cycle; the follicular phase, the ovulatory phase, and the luteal phase. Within the follicular phase you have the menstrual phase and the proliferative phase.

The menstrual phase, commonly known as the “period”, begins the cycle when the uterine lining (or endometrium labeled above) sheds. Cycle day 1 (CD1) is the first day of the menstrual period. The proliferative phase is the rebuilding of the uterine lining. It is also the time when your brain signals to your ovaries to begin developing the next egg for ovulation. The ovulatory phase, or ovulation, is the release of the egg from the ovary into the fallopian tubes for fertilization. The luteal phase/secretory phase is when the corpus luteum, left behind by the egg, secretes progesterone. And the uterine lining prepares for the possibility of implantation of the fertilized egg.

If implantation does not occur then the hormone levels drop, ending the luteal/secretory phase and the current menstrual cycle. And beginning the next menstrual phase.

So what about the 28 day cycle myth?

In the 28 day cycle model, both the follicular phase and the luteal phase are considered to be 14 days long. With ovulation occurring on cycle day 14 (CD14), and the total cycle being 28 days long. While the average cycle length may be 28 days, not everyone will experience 28 day cycles. Anywhere between 26 and 35 days is considered normal. But it’s not uncommon for cycles to last more than 30 days.

This fact is pretty widely known, so how is the 28 day cycle myth still perpetuated? Even if you experience a 28 day cycle, you may not actually ovulate on CD14. The ovulation on day 14 myth is more ingrained than the 28 day cycle myth. Both the follicular and luteal phases can vary quite a lot person to person and even cycle to cycle.

The follicular phase can be as short as 8 days, making conception from sex during your period a possibility. And for some people, the follicular phase can last many months if lack of ovulation is a problem.

While the average luteal phase is considered to be 14 days, a healthy luteal phase can be anywhere from 12 to 16 days. And for some can last anywhere from 4 days to 17 days, or even longer with certain health conditions.

We’ll look at some of the issues with this in Part 2. Want to know when part 2 is available? Sign up for the newsletter below!



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