You’ve likely read or been told that fertility awareness methods (FAMs) are just another name for the “Rhythm Method,” which isn’t very effective for pregnancy avoidance. Misinformation about fertility awareness is sadly so ubiquitous that if you’ve ever brought up FAMs with your doctor, he or she may even have referred to them collectively as the “Rhythm Method.” Maybe you’ve even Googled “natural birth control” and the Rhythm Method came up in your search results, further cementing that they are one and the same. So, are “natural family planning” and “fertility awareness methods” just code names for the Rhythm Method?
The truth is, the Rhythm Method was a precursor to modern, evidence-based fertility awareness methods (FAMs) of natural family planning (NFP). It’s also true that not all fertility awareness methods are created equal in terms of their effectiveness for couples specifically seeking to avoid pregnancy.
Let’s look into what the Rhythm Method actually is, so that we understand how it led to the development of the highly effective, modern FAMs we have today, and more importantly, how the Rhythm Method differs significantly in the type of data it collects—and therefore in efficacy—from modern FAMs.
What is the Rhythm Method?
At its most basic, the Rhythm Method, also called the calendar method or calendar rhythm method, is “ a way of lowering your chances of getting pregnant by avoiding [intercourse during] the middle of the cycle, when ovulation generally occurs on the average, for the average woman.”
In the 1920s, Japanese gynecologist and surgeon Dr. Kyusaku Ogino and Austrian OB/GYN Dr. Hermann Knaus each independently discovered that ovulation occurs roughly two weeks before the next menstruation, and posited that the egg released during ovulation had a limited lifespan of a day or less. With this new knowledge of female fertility, Chicago-based OB/GYN Dr. Leo Latz published “The Rhythm of Sterility and Fertility in Women” in 1932, which advocated that couples seeking to avoid pregnancy stay abstinent around the projected time of ovulation. With those simple facts, the “Rhythm Method” was born.
The Rhythm Method uses a woman’s longest and shortest cycle lengths over the previous six months to calculate when her next period will come, and therefore when she might expect to ovulate next. This rudimentary method works best for women with very regular cycles, and less well for women with irregular or long cycles. However, even women with regular cycles can have the occasional long or irregular cycle because of emotional stress (like a big test or a move) or physical stress (like an illness). The Rhythm Method’s positives include its low cost and lack of physical side effects for the woman. Its main drawback is a failure rate of 24% (which means that out of 100 women using the Rhythm Method to avoid pregnancy, 24 of them will unintentionally become pregnant within one calendar year).
Unfortunately, many women have been scared away from exploring FAMs altogether because of the CDC’s long-standing, inaccurate website content lumping the effectiveness of all FAMs in with the inferior efficacy rate of the Rhythm Method. Until 2019, the CDC’s website gave a 24% failure rate for all FAMs. The website has since been changed to reflect an efficacy range of 2-23% for FAMs, reflecting the difference in effectiveness rates between natural methods (but still mistakenly conflating FAMs with the rhythm method).
What’s the difference between a fertility awareness method (FAM) and the Rhythm Method?
While calendar-based methods such as the Rhythm Method use historical cycle lengths and, sometimes, a predictive algorithm to estimate when a woman’s next period is coming, modern FAMs rely on a woman’s daily observations of her unique body’s fertility biomarkers. A woman trained in an evidence-based FAM can confidently identify her body’s real-time fertility or infertility, and use that information to time or avoid intercourse based on pregnancy intention. Because they are based on the individual woman’s daily health data, modern FAMs can work for women with long or irregular cycles, including during times of stress or illness, and are far more effective than calendar-based methods of NFP.
WATCH: How modern FAMs and NFP are *not* the Rhythm Method // Lisa Hendrickson-Jack – YouTube
Modern versions of the Rhythm Method
Standard Days Method
While the Standard Days Method is newer, having been developed in 2002, both the Rhythm Method and the Standard Days Method fall under the umbrella of calendar-based methods of natural family planning. That is, both work primarily for women with regular cycles, and neither one tracks any biomarkers of fertility. As we’ve previously noted, “The standard days method is for a woman whose cycles range from 26 to 32 days in length, and it predicts she’ll be fertile for days 8-19 of her cycle. With the standard days method, the perfect use failure rate is 4.75% and the typical use failure rate is reported as 11.96%.”
CycleBeads
You may also have heard of CycleBeads, which are a tool to remember the expected days of fertility and infertility in the woman’s cycle based on the Standard Days Method. Like some FAMs, the CycleBeads website recommends using condoms to prevent pregnancy if a woman has sex on her known fertile days. Natural Womanhood does not recommend this practice for women truly seeking to avoid pregnancy for reasons thoroughly discussed here.
Clue Birth Control App
Separate from the regular Clue app, the Clue Birth Control app is an FDA-approved natural birth control option for women with regular cycles. Clue is a calendar-based method app that uses a predictive algorithm based on the woman’s previous cycle lengths to determine when her next period should be coming. Because calendar methods do not track any biomarkers, women using the Clue app miss out on the body literacy that comes with learning to track biomarkers of fertility.
As we reported back in March, the FDA approved the Clue Birth Control app specifically “for contraception for women ages 18 – 45 years old, to monitor their fertility and prevent pregnancy. Clue Birth Control is suitable for women with predictable 20 – 40 day cycles, who have not recently used hormonal birth control.” Pregnancy avoidance effectiveness rates were slightly higher for Clue BC app users than for Standards Days or CycleBeads users, with a 3% perfect use failure rate and 8% typical use failure rate.
Which are the modern, evidence-based FAMs?
Again, if a method is asking you to track some kind of biomarker, it is a FAM. As we’ve stated before, some FAMs are more effective than others, and some FAMs will include more biomarkers for more accuracy in pregnancy avoidance.
Modern, evidence-based FAMs fall into three categories. As their name suggests, mucus-only options rely on cervical mucus observations alone. Symptothermal methods utilize both cervical mucus observations as well as a basal body temperature crosscheck, and sometimes include an optional cervical os (opening) check. The third category, symptohormonal methods, utilizes both cervical mucus observations and urinary hormone metabolite levels, typically as measured by some kind of fertility monitor or test strip. See our “FAM” and “Learn a Method” homepages to look into each of these methods and their effectiveness rates, as well as to determine which might make the most sense for your situation.
This article was updated on July 20, 2024 with a new link for the effectiveness of the Standard Days Method.
Additional Reading:
FAM Basics: What is Cervical Mucus?
FAM Basics: Everything You Need to Know about your Endometrium
FAM Basics: Basal Body Temperature (BBT)
