August 21, 2018

A multidisciplinary team undertook a comprehensive review of the published evidence of FABM effectiveness for avoiding pregnancy. It was published earlier this month in the Green Journal, the official publication of the American College of Obstetricians and Gynecologists (ACOG). This article follows the previous FABM literature review published by FACTS members in 2013. Although both reviews are rigorous, some critical differences warrant deeper scrutiny.

The current review, led by Dr. Rachel Urrutia with University of North Carolina and Reply Ob/GYN, covered any study on FABM effectiveness published in a peer-reviewed journal in one of four languages as of June 2017. Studies were included if they met 3 simple criteria: prospectively collected information on pregnancy intentions, tracked pregnancy outcomes, and followed at least 50 participants. Over 8,700 citations were identified; from these, more than 400 publications were assessed for eligibility. From these publications, the team identified 74 between 1951 and 2017 that covered 53 distinct cohorts for in-depth evaluation.

Using best practices from evidence-based medicine and building on earlier systematic reviews, the authors created a grading scale to evaluate the quality of studies employing FABMs to postpone pregnancy. Their scale included 13 items (Appendix 4), each of which could be ranked high, moderate, or low quality. For a study to be considered high quality it needed to be ranked high in all 13 criteria, and it would be scored as low quality overall if any 1 of the 13 items was scored low.

This scale proved to be extremely rigorous as none of the studies was graded high (i.e. none received a perfect score in all 13 categories), 21 were judged moderate quality, and 32 were judged low quality. Several appendices (137 pages when downloaded) provide the justification for each study’s rating and are available online.

A closer look at the grading scale reveals that to be scored high quality in the statistical analysis item, cycles where intercourse was not documented were to be excluded from the analysis. Only 1 study met this criterion, Trussell’s re-analysis of the WHO multi-country study¹, so this single item disqualified the remaining studies from consideration as high quality.

While one can understand the logic of excluding these cycles (based on an assumption that pregnancy would not be possible without intercourse), the approach seems contrary to the underlying principles of FABMs where informed, shared-decision making and development of self-control are integral to the use of the methods. Couples may choose not to have intercourse in any given cycle for many reasons, such as the variability in the woman’s cycles, comfort level of couples with interpretation of their fertility signs, and/or personal or professional obligations that may not allow them the time or opportunity to have sexual relations. Since abstaining from sexual relations during potential days of fertility is among the guidelines for using FABMs, it seems unfair to downgrade studies in which couples may simply have followed the rules. Furthermore, it is not at all clear whether ANY contraceptive method, be it hormonal, a device or surgical, has ever been evaluated with this criterion and would meet this definition of high quality. While this may be an ideal criterion to include, it is uncertain this standard has ever been required before now.

Despite this debatable decision regarding what cycles to include or exclude, the study reveals there are differences in FABM effectiveness between different methods when considering data from moderate quality studies. Typical use unintended pregnancy rates range from <5% to 33% across the 11 different types of FABMs identified by the authors. Perfect use rates have rarely been calculated correctly but, when reported, they are consistently lower than 5%, and some less than 2%. The wide range of effectiveness rates reinforces the inappropriate use of a single number to classify FABM effectiveness, such as the 24% figure commonly quoted by the CDC, which is based on retrospective studies that would not have met the inclusion criteria used in this review.

While this important review highlights the ongoing need for well-conducted research on all fertility awareness based methods, a major concern is that this study will be used by many to reinforce the myth that FABMs don’t work. The “In Brief” summary on the journal’s website makes this clear. Here’s what it says of the study:

“Prospective studies evaluating the effectiveness of specific fertility awareness–based methods to avoid pregnancy are of low to moderate quality; effectiveness estimates vary between and among methods”.

A more positive perspective on this review is that it calls for more focused work on FABMs as extremely promising approaches to family planning. After all, about 10 “moderate-quality” studies consistently demonstrate the potential for effectiveness rates rivaling hormonal contraceptives with none of the side effects and at significantly lower costs to users and insurers. If this were an intervention for Alzheimer’s disease or diabetes, the investors would be lined up around FABM providers offering support to prove their worth.

Beyond this, it is important to recognize that effectiveness is only one of the factors that matter to women when choosing a family planning method. The side effect profile and the burden of responsibility, which falls almost entirely on women, also make a difference. FABMs clearly stand out over other family planning approaches in these areas. Indeed, the World Health Organization recognizes FABMs as the only family planning methods with no adverse side effects.² A single-minded focus on effectiveness to postpone pregnancy dilutes the potentially larger benefits of FABMs.

The review ends with this statement, “Fertility awareness-based methods will continue to be relevant and important for many people for a variety of reasons; obtaining the best possible data, and documenting use in varying populations, is critical.” With this final assessment and recommendation, we agree!



  1. Lamprecht, V, Trussell, J “Natural family planning effectiveness: Evaluating published reports.” Advances in Contraception 13(2/3): 155-165, 1997.
  2. Festin MPR, Kiariea J, Solo J, Spieler J, Malarcher S, Van Look PFA, Temmerman M. Moving towards the goals of FP2020 — classifying the goals of contraception. Contraception. 2016; 94: 289-294.

Pin It on Pinterest