Addressing Criticisms: A Call for Clarity about the Effectiveness Rates for Individual FABMs

May 17th, 2017

The FACTS/ Natural Womanhood petition asking the Centers for Disease Control and Prevention (CDC) to change its approach to reporting effectiveness rates of FABMs is getting noticed. One response in a May 4, 2017 blog post by Chelsea Polis, a reproductive health epidemiologist with particular interest in fertility awareness based methods (FABMs), defends the current CDC approach:

“In sum, the petition asserts bias and lack of scientific rigor in current research findings and implies that the CDC is misleading people, when in fact, there are sound scientific reasons for the CDC’s approach to communicating the range of contraceptive options available and the evidence to-date of their contraceptive effectiveness.”

Dr. Polis lists 5 clarifications in support of this assertion. We applaud the additional attention and insight these points bring to the discussion. We believe her points reinforce the urgent need to bring additional research and transparency to the expected real world effectiveness of various FABMs. At the same time, we remain concerned about the way the data are currently represented on the CDC website, and in their source, the summary table that appears in Contraceptive Technology.

The 24.0% typical use pregnancy rate reported by the CDC for FABMs is based on data from the U.S. National Survey of Family Growth (NSFG), a rigorously designed and carefully conducted ongoing survey of women’s and men’s experiences with family planning, reproduction, and related matters. Because few women in the population-based survey are using FABMs, women using any and all identified FABMs were combined together to calculate a typical use pregnancy rate for FABMs. Consider further that an unspecified version of calendar rhythm, the oldest natural method, is used by 8 in 10 women in the pooled sample. In contrast, most modern FABMs rely on real-time observation of biomarkers of the fertile window.

Therefore, we believe the fundamental question is as follows: is it reasonable and informative for clinical counseling to combine different methods of FABMs together to estimate one typical use pregnancy rate?

As a thought experiment, consider: would it be reasonable and informative for clinical counseling to combine women/couples who were using the male condom, the female condom, and the diaphragm together for one typical use pregnancy rate for barrier methods? Even if 80% of couples were using the male condom? The different methods of fertility awareness are arguably at least as different from each other as these different barrier methods. There are very different perfect use pregnancy rates for several different FABMs, which suggests that the typical use pregnancy rates may also be different.

Again: is it reasonable and informative for clinical counseling to combine different methods of FABMs together to estimate one typical use pregnancy rate?

We believe that is the fundamental issue.

At the same time, in the FABM community, we must acknowledge that most of the studies that have been done with FABMs are of select, albeit diverse populations, and may not represent the breadth of experience with these methods. Efforts to improve the understanding of the experience and outcomes of the use of these methods across broader populations should be encouraged and research funding made available. The data available to date suggest that pregnancy rates with FABMs are highly influenced by demographic and social factors and underlying childbearing motivations of the persons using them, more so than most other family planning methods.

Perhaps the language of the petition and some of the support for it have been impassioned bordering on polemical, but the goal of the petition is to raise awareness and ask the CDC to provide accurate information about effectiveness rates for individual FABMs. While we wish to affirm that the NSFG is a well-designed and carefully conducted study that provides valuable data for many questions, we do not believe it can currently answer the question of typical use pregnancy rates of the modern methods of FABMs.

We hope that the petition will give a voice for FABM users and advocates in a way that will ultimately contribute to constructive dialogue and better research.

In conclusion, we fully agree with Dr. Polis’ concluding statement that it is certainly important to acknowledge that a great deal of misunderstanding exists around FABMs, and that clear communication about these methods is necessary. For example, helping people understand the distinctions between the rhythm method and other FABMs (such as the sympto-thermal method, the TwoDay method, Standard Days method, Billings Ovulation method, sympto-hormonal methods such as Marquette, and other methods) would be useful in dispelling the misunderstanding that all women using fertility awareness based methods (or “natural family planning methods”) are using the rhythm method.

Finding productive and accurate ways to communicate about these methods is important, and will take collaborative efforts to achieve.

by Joseph Stanford, MD, and Michael Manhart, PhD
Dr. Stanford and Dr. Manhart are members of the Advisory Council for FACTS.