Natural Family Planning and Fertility Awareness – not the old “Rhythm method”!

This article was and is meant to clarify the several terms and to help you with understanding the basics. For these and other pertinent terms, you may refer to the Alphabet of bioZhena at /2007/11/28/the-alphabet-of-biozhena/ (a glossary/primer with clickable table of contents).

Like The Alphabet of bioZhena, this article was originally published in 2007. Now, in 2020, we observe that the various apps of the smartphone era would represent progress compared to charting daily data on paper, but unfortunately the apps are invariably based on the decades-old methods of monitoring inadequate observables (hinted at below).

This is highly pertinent because by 2020 many women are concerned about the unwanted effects of “the Pill” and of the derivative contraceptives. Many, particularly young, women are looking for non-hormonal alternatives, looking chiefly online, mostly with their smartphones. The headline of a 2019 Politico article summed up the situation: Fertility-tracking apps: Popular, hyped — and often inaccurate.

Now for the terminology.

Natural family planning (NFP):

This refers to several fertility awareness methods for spacing, postponing, avoiding or enhancing the possibility of conception, without any chemical or physiological alterations of the reproductive system (female or male). NFP, therefore, is not merely a pregnancy prevention method but is also utilized to increase the chances of becoming pregnant.

Natural family planning research has shown that among the advantages of the NFP practice is that the required discipline enhances the sexual relationship and dialogue, and that there is a reduction of “dominant attitude” in both men and women practicing NFP.

Contemporary methods are sometimes referred to as ‘fertility awareness’ (FA; or FAMs, Fertility Awareness Methods; or FABMs, Fertility Awareness Based Methods) since they are ultimately based on awareness of symptoms of fertility that are, or may be, recognizable, detectable or measurable by any woman.

Other people distinguish between NFP and FA in terms of the fertile phase of menstrual cycle (aka fertile window): NFP users abstain from sex whereas FA users employ a barrier method of contraception during the fertile phase.

In any case, NFP and FA are distinct from the older ‘calendar’ methods such as Ogino-Knaus (the so-called ‘rhythm’ method, explained below). The two MDs – Drs. Ogino and Knaus – independently discovered in 1936 that women can only get pregnant during a few days in what was said to be the mid-cycle (“mid-cycle” is rarely the correct expression in reality, as is also rare the 28 days length of the menstrual cycle assumed in the expression).

The American College of Obstetricians and Gynecologists (ACOG) referred in more recent years to “family planning by periodic abstinence” and explained that this is [QUOTE] “another name for the method of birth control that used to be called ‘rhythm method’ or ‘safe period’. More recently it has also been called ‘natural family planning’ or ‘fertility awareness’. It isn’t a single method but a variety of methods. Each is designed to help a couple find out which days during a woman’s menstrual cycle she is likely to be fertile or able to become pregnant” [END OF QUOTE]. The referenced article was in – no longer available.

While the proponents of NFP warned that, without further expenditures on education, NFP would remain a fringe method in the U.S. (unlike in various other countries), the American College of Obstetricians and Gynecologists advised the public that [QUOTE] “periodic abstinence is quite an effective means to prevent an unwanted pregnancy” [END OF QUOTE]. Proponents of NFP further expressed the hope that a better technique of assessing the fertile window would become available.

A detailed and well informed article by a family medicine practitioner  was published in American Family Physician by John H. Geerling, MD [Am Fam Physician 1995 November 1;52(6):1749-56, 1759-60] who stated that “studies have reported that women who practice methods of natural family planning do so for health reasons, and because the methods are natural and do not require the use of chemicals”. He also wrote that: “Effective use of natural family planning requires teaching beyond that which physicians can provide during a typical office visit.”


The OvulonaTM from bioZhena is designed to make NFP/FAM easy to practice and accessible to anyone – without teaching.



FAM (fertility awareness method):

A method of determining a woman’s daily fertility status through self-assessment of certain fertility signs: waking temperature (also called the basal body temperature or BBT), assessing vaginal fluid wiped off the vulva (vaginal opening), and cervical position assessed by fingering the cervix (at the top of the vagina). FAM also allows for use of the results of urine testing for one or two sex hormones. While NFP users abstain, FAM users apply one of the barrier methods of contraception (such as a condom) for vaginal intercourse during the “unsafe days” of the woman’s menstrual cycle (the fertile phase).

Invariably, to be on the safe side, the extent of the “unsafe period” of “unsafe days” is made excessive by commercial products working with the inherently inaccurate self-assessment data, in order to minimize the occurrence of unwanted pregnancy. That, not surprisingly, turns out to be counterproductive. Many couples do not obey the too-long “unsafe period”, with unwanted consequences.


The OvulonaTM from bioZhena is designed to make NFP/FAM easy to practice and affordable for anyone. Our mission includes reliable and accurate electronic determination of the 3-day fertile window.

Ovulona - single slide 3-day fertile window click for better eligibility in animated PPS slide

The determination is electronic (and display will indicate either “Infertile” or “Fertile Day #1, #2 or #3 = Ovulation”). This will not require any data interpretation by the user. The measured raw data is shareable with the woman’s healthcare provider(s) for better diagnosis.


As opposed to the old “Rhythm” method:

Also called the calendar method, it has been discredited because of two factors: its unwarranted assumption of regularity of menstrual cycles, and the long period of abstinence demanded by it. The method’s one-time well-known status has caused a skeptical bias in America to all NFP or FAM methods, although they are very different.

The calendar or “rhythm” method is useless (and silly), unlike NFP or FAM (with a proper tool). The reader may be aware of another nickname for the “rhythm method” (Vatican Roulette, anyone?)… If so, you also understand that the above-referenced ACOG is confused when they talk of “another name for the method of birth control that used to be called ‘rhythm method'”. This sort of confusion is sadly not unique, and there are references to other instances in The Alphabet ( /2007/11/28/the-alphabet-of-biozhena/ ).

For more about how the “rhythm method” came about and how its failure helped to bring about the chemical pseudo-hormone contraception, see the 2012 blog post Why too many young and not so young ladies could NOT receive flowers on Mothers’ Day: Why so many trying-to-conceive, why so much infertility. (Say thank you to the social and medical advances of the twentieth century – primarily those of chemical birth control, the Pill.)

The Pill that suppresses ovulation and thus suppresses the naturally biosythesized sex hormones that women need for good health.

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2 Responses to “Natural Family Planning and Fertility Awareness – not the old “Rhythm method”!”

  1. Variability of menstrual cycles and of ovulation timing « bioZhena’s Weblog Says:

    […] because they experienced difficulties in achieving pregnancy, or because they wanted to learn NFP [Natural Family Planning] as a means of birth control. Or, maybe, they wanted to use NFP for both, at different phases of […]

  2. What is the mechanism of stress and how does it affect reproduction. An update. « bioZhena's Weblog Says:

    […] By emphasizing the critical timing of stress, this paper points by implication at the importance of routine Ovulona monitoring of Folliculogenesis In Vivo™, particularly  for assisting women who have difficulty to conceive but also for those practicing natural birth control. […]

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