The Day 14 Myth

Natural family planning seems to be one of those things many people have heard of, but practically nobody understands except the people who use it. My wife and I have used it, and it hasn't failed us. It's a pretty simple system of fertility awareness. You use simple observations to tell where you are in the menstrual cycle. In fact, once you get the hang of it, it becomes easier to think of the menstrual cycle as what it really is: the ovulation cycle. At least that term makes more sense to me, since it describes the process that's really happening in women's bodies, rather than just the most obvious outward sign of it.

Because it's fertility awareness, it can be used both to avoid and to achieve pregnancy. Or it can be used simply to know what's going on. In fact, both the simplicity and the many practical uses of it make one wonder why nobody uses it in modern healthcare.

Consider the woman who has an "abnormally" long cycle, longer than the textbook 28 days. If she's concerned about this and mentions it to her doctor, she'll likely get put on birth control pills. But birth control pills just produce a fake cycle; it stops everything your body is doing, and once a month you take fake pills which let you bleed something like a menstruation. Why is the doctor so concerned with a 28 day rigidity? There's nothing wrong with the woman. The only benefit I can see is the assurance you won't "randomly" get pregnant or have your period, which you can tell without pharmaceuticals by using fertility awareness. That's because, "irregularity" aside, nobody has a random cycle.

Or say she wants to get pregnant. She'll be referred to a fertility specialist who will also, bizarrely, presume a 28 day cycle. Her hormone levels and other factors will be checked around when she's supposed to be ovulating, to see if everything is working correctly. Unfortunately, to most doctors, she's supposed to be ovulating on Day 14 after her last period. Since this might be nowhere near when she's really ovulating, her results be inaccurate, and further medical decisions will be made based on wrong information.

Or say she does get pregnant. She'll go to an obstetrician and be asked about her last menstrual period. Then her due date will be calculated using a simple wheel device, tacking on an extra two weeks to account for the two weeks between textbook period and ovulation. Except what if she ovulated three or four weeks after her period? Her due date could be set weeks early, leading to unnecessary tests, or induced labor for being "late," and a premature underweight baby. In fact, if you use fertility awareness and know when you conceived, some people advise "fooling" your standard-issue obstetrician by making up your own LMP date two weeks before you conceived just so you have an accurate due date!

All of these misguided medical judgments (can I say medical errors?) are based on a bizarre myth: that the standard woman ovulates on Day 14 of her cycle. There's no scientific basis for this. Even if it is common, it's not nearly common enough to be applied to all women.

Even though these physicians all studied and can presumably remember how the whole female reproductive cycle works, how follicle-stimulating hormone and luteinizing hormone are produced by a woman's pituitary gland, how estrogen and progestin shift, how the uterine lining depends on these hormones to grow and shed, how cellular miosis occurs and how a woman's haploid gametes form, how an egg is produced and travels and is fertilized, how the corpus luteum and early placenta produce hormones to sustain a pregnancy; even though they know all this, they presume a Day 14 ovulation and take a chance at throwing all their real-world clinical judgments off. Little of that textbook knowledge matters if you base your real clinical decision-making on a myth.

Guess the unscientific portion of this menstrual cycle diagram.

I suspect that part of the problem with using fertility awareness in modern medicine is that it requires significant time devoted to teaching and answering questions (prescribing the Pill is much quicker, and I doubt physicians are reimbursed for teaching fertility awareness), and that it depends on the woman observing and tracking herself, and not the physician or the labs.

If you've experienced this, please comment and share your story. And if you've seen the opposite, doctors and other clinicians who don't presume a Day 14 ovulation or who know anything at all about fertility awareness, please share their stories as well. It would certainly be heartening.