To the Editor:

We appreciate Dr. Paradise and colleagues including current information on fertility awareness–based methods in their article about evidence-based contraception.¹ We would like to clarify some information needed for family physicians to effectively offer these important options to patients who want to avoid pregnancy without the use of hormones or devices.

The article states that patients with irregular menstrual cycles should avoid fertility awareness–based methods. Two systematic reviews of fertility awareness–based methods from 2018 and 2013, cited in the article which used the U.S. Preventive Services Task Force and SORT criteria, respectively, support methods that include the observation of fertility biomarkers that can be effective in patients with irregular cycles.^2,3 Data also suggest fertility awareness–based methods can be effective in patients who are lactating, although additional data are needed.⁴

With correct use, the unintended pregnancy rates for individual methods available in the United States range from less than 1 to 5 pregnancies per 100 women-years.^2,3 Methods with dual identifiers of ovulation have the lowest correct use pregnancy rates, specifically when intercourse is restricted to the postovulatory phase of the cycle.⁵

The wide range of typical-use pregnancy rates of fertility awareness–based methods depends on the user and specific method. User motivation, partner support, and appropriate education are critical factors that can influence unintended pregnancy rates during typical use. The general education level of the patient is not a factor. To date, the lowest correct or typical-use pregnancy rates have been demonstrated when patients learn the method from trained educators; therefore, clinicians must provide accurate information about the methods and appropriate referrals to trained instructors. Although more than 500 fertility tracking apps may facilitate cycle tracking, only two (Natural Cycles, Clue Birth Control) have been evaluated for effectiveness in avoiding pregnancy. Other apps should not be solely relied on for preventing pregnancy.⁵

Although the website cited for counseling patients about fertility awareness–based methods (https://www.rhntc.org) has educational videos for clinicians, it does not have patient education materials about individual methods. Additional evidence-based patient education materials for choosing among different fertility awareness–based methods are available via video and print in English and Spanish at https://www.factsaboutfertility.org/what-is-charting.

In Reply:

Thank you for the thoughtful letter and clarifying information. Although fertility awareness–based methods of contraception represent a reasonable option for those who want to avoid hormonal methods, like all contraceptive methods, they require frank counseling from knowledgeable clinicians about their effectiveness and eligibility criteria.

Fertility awareness–based methods that rely on standard intervals of fertility (e.g., Standard Days Method) require predictable menstrual cycles; therefore, any abnormal uterine bleeding causes those methods to be unreliable. Many trials of symptoms-based fertility awareness–based methods that rely on fertility biomarkers (e.g., cervical mucus, basal body temperature, urinary hormones) include participants with abnormal bleeding patterns in their effectiveness calculations; however, high-quality, prospective data on how these methods are affected by irregular cycles are limited.¹ Although it is reasonable to assume that these methods should be unaffected by cycle length, the Centers for Disease Control and Prevention recommends fertility awareness–based methods (including those that are based on symptoms) be delayed until the abnormal uterine bleeding is evaluated and treated.²

Fertility awareness–based methods have been successfully implemented in low-resource settings and populations with low literacy, with perfect-use pregnancy rates ranging from 0.0 to 12.1 pregnancies per year.^1,3 However, relying solely on perfect-use pregnancy rates when counseling patients may provide a false sense of security and underrepresentation of the actual pregnancy risk. Discussion of any contraceptive method's effectiveness requires a discussion of real-world pregnancy rates from the literature.

Many individuals use fertility awareness–based methods to prevent pregnancy; despite this, clinicians report insufficient training and hesitancy to counsel their patients on these methods.⁴ Encouraging familiarity with the different fertility awareness–based methods and empowering clinicians in counseling or referring patients to trained instructors are vital to address this unmet need in individuals looking for an alternative to hormonal contraception who are motivated and have partner support.

The views expressed in this publication are those of the authors and do not necessarily reflect the official policy or position of the U.S. Navy, U.S. Air Force, U.S. Department of Defense, or the U.S. government.