May 30, 2022

Effectiveness of Fertility Awareness-Based Methods: What are the facts?


Editor’s Note: As we commemorate those who have given their lives while serving in the United States Armed Forces this Memorial Day Weekend, we highlight a review article summary written by a Family Physician who served in the Air Force. She wrote this summary as part of the FACTS elective, which she completed while finishing her master’s degree in bioethics.  The original article, Misrepresentation of Contraceptive Effectiveness Rates for Fertility Awareness Methods of Family Planning by Dr. Joseph Turner, provides an overview of various fertility awareness-based methods (FABMs) and highlights a common challenge: the lack of accurate information about the effectiveness of these methods.

Also, be sure to read the latest piece published by our executive director, Dr. Marguerite Duane, lead author of a research article entitled, Fertility Awareness-Based Methods for Women’s Health and Family Planning, which provides the most up to date evidence on the effectiveness of FABMs.



Many medical students and trainees agree: “Learning medicine is like drinking from a firehose.” Medical literature is constantly updated as the volume and speed of scientific and technological discoveries increase. This has significant implications on the study and practice of medicine, most clearly expressed in the increasing emphasis on Evidence-Based Medicine — a term coined in the early 1980s. To keep up with the ever-increasing repository of medical research, physicians have come to rely more and more on guidelines produced by medical societies. A by-product of this paradigm is that interventions and treatment without high quality evidence are either understated or, even worse, excluded from these guidelines. This has been especially true in the application of fertility awareness methods* (FAMs) or fertility awareness-based methods* (FABMs) in the avoidance of pregnancy, where high-quality prospective studies have been less abundant than for hormonal and barrier methods. This 2020 article critically reviews the method effectiveness and typical-use effectiveness of FABMs and how that data is represented in the medical literature and clinical guidelines [1].

MethodologyThis review of FABMs effectiveness rates includes analyses of international literature from the World Health Organization (WHO), Centers for Disease Control (CDC), key clinical studies, and recent systematic reviews of FABMs.


Variability in study design, low quality clinical trials, and use of inaccurate conglomerate data for a combined group of FABMs have led to a misrepresentation of FABM efficacy rates in the medical literature and clinical guidelines. A 24% failure rate of FABMs is frequently cited based on retrospective reviews from 1995 and 2002, which combined data from a variety of FABMs, including methods with low efficacy and high efficacy, such as the Rhythm method and the Billings Ovulation Method, respectively [2]. Accurate representation of FABMs’ effectiveness rates requires a critical review of the quality of the data and studies, as well as separate effectiveness rates for each of the major FABMs: the Billings Ovulation Method, the Creighton Model System, the Marquette Method, the Sympto-Thermal Method, the Two Day Method, and the Standard Days Method.

“Accurate representation of FABMs’ effectiveness rates requires separate effectiveness rates for each of the major FABMs”

This article included the review by Manhart et al. that utilized the Strength of Recommendation Taxonomy (SORT) criteria to evaluate the quality of FABM effectiveness studies [3]. This review identified 29 studies of FABM effectiveness and found method efficacy rates ranging from 95.2% with the Standard Days Method to 100% with the Marquette Method. Typical use effectiveness rates ranged from 86% with the Two-Day method to 98% with the sympto-thermal method. The Turner review also included six studies from China  which evaluated the Billings Ovulation Method (BOM)  and used randomized controlled trials and cohort studies over the past 20 years, demonstrating effectiveness rates of 97 to 99% [[4][9]]. However, it should be noted that these studies included some women with limited fertility over 50 years of age and in perimenopause, and some included criteria requiring 6 to 9 months of BOM use in the pre-study time period.


This review raises several considerations. FABM effectiveness data from high quality studies, as defined by SORT Level 1 criteria, is necessary to ensure accurate comparisons of contraceptive methods in clinical guidelines. The perpetuation of inaccurate data decreases medical professionals’ willingness to learn about, recommend or discuss these methods with patients and limits women’s access to safe and effective FABMs.

“The perpetuation of inaccurate data decreases medical professionals’ willingness to learn about, recommend or discuss these natural methods with patients and limits women’s access to safe and effective FABMs.”

Second, the review of the Chinese studies raises important points. With governmental policies limiting child-bearing, why would a country that limits family size allow studies of FABMs unless those methods were thought to be effective, safe, and cost-effective? There would not be incentive to use these methods unless high efficacy was possible. However, generalization of the efficacy rates from China is difficult to do, given governmental policies, limited publication of studies in Western literature, variability in participant inclusion criteria, and a cohort of highly motivated FABM users. All these factors may have positively affected typical-use efficacy rates. Ethically-speaking, a randomized controlled trial of FABMs, as done in some of the Chinese studies, would be problematic in the United States, as participants who desired to use FABMs could be assigned to use other methods instead or vice versa, thus affecting motivation and, potentially, effectiveness rates.

Third, additional well-conducted prospective studies of FABMs could help ensure high-quality studies and minimize variability in study design and methodology.  Retrospective studies may be affected by missing data and recall bias. However, given that there is generally neither a product (such as an IUD) or a prescription (such as an oral contraceptive pill) involved, it could be challenging to obtain funding for prospective studies. Of the individual studies reviewed in this article, all were listed as either low or moderate quality. To increase clinician and patient confidence in these methods, prospective quality trials would be necessary to evaluate FABM efficacy rates with the highest level of scrutiny.

* Executive Director’s Note: Terminology in this field has been evolving, and it is important to provide further clarity.  Originally, the term “natural family planning” or NFP was coined in 1974 by the National Institutes of Health (NIH) and ​​is defined by the World Health Organization as “methods for planning or avoiding pregnancies by observation of the natural signs and symptoms of the fertile and infertile phases of the menstrual cycle.”  The term fertility awareness-based methods highlights that this information can also be used for monitoring a woman’s reproductive health and may be used interchangeably with the term natural family planning (NFP) [10].  The term “fertility awareness methods” was popularized in the book, Taking Charge of Your Fertility, and commonly refers to the Sympto-Thermal Method with or without barriers.


[1] Turner J. (2020). Misrepresentation of contraceptive effectiveness rates for fertility awareness methods of family planning. J. Obstet. Gynaecol, 47(7), pp.1-7. doi: 10.1111/jog.14593

[2] Manhart M. D., Duane M., Lind A., Sinai I., Golden-Tevald J. Fertility awareness-based methods of family planning: a review of effectiveness for avoiding pregnancy using SORT. Osteopathic Family Physician 2013; 5 (1): 2-8.

[3] Kost K, Singh S, Vaughan B, Trussell J, Bankole A. (2008). Estimates of contraceptive failure from the 2002 National Survey of Family Growth. Contraception, 77(1), pp.10-21.

[4] Feng XJ, Guo H. (2005). Billings natural fertility regulation: followup analysis of 320 cases. Tibet Medical J, 26(1), pp. 48–49.

[5] He XH, Chen J, Liang SL. (2009). Study on the clinical effect of Billings method™ of natural family planning. Jiangxi Med J, 44(1), pp. 475–477.

[6] Jin BH, Yang ZJ, Xu JX et al. (2004). 654 women of childbearing age use the Billings ovulation method for one year. Reprod Contracept, 24(1), pp. 154–156.

[7] Lu AI, Li LH, Ge XY. (2011). Analysis of clinical effects of Billings Method™ of natural family planning. Med Inform, 24(1), pp. 3697–3698.

[8] Qian SZ, Zhang DW, Zuo HZ, Lu RK, Peng L, He CH. (2000). Evaluation of the effectiveness of a natural fertility regulation programme in China. Bull Ovul Method Res Ref Cent Aust, 27(1), pp. 17–22.

[9] Wang Y. (2014). Analysis of the application effect of Billings natural contraception in community women’s health care. Primary Medical Forum, 18(1): 1348–1349.

[10] Duane M, Stanford JB, Porucznik CA and Vigil P (2022) Fertility Awareness-Based Methods for Women’s Health and Family Planning. Front Med9:858977. doi: 10.3389/fmed.2022.858977

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