Natural Family Planning Week

Effectiveness of FABMs to Avoid Pregnancy: A Review of Research

By: Jenna Starke, MD

Director’s Note: This week, we celebrate Natural Family Planning Week and all the natural methods available to women and couples! With numerous modern fertility awareness-based methods (FABMs) and various biomarkers to track, users need reliable information about each method’s effectiveness for family planning. Dr. Marguerite Duane, executive director of FACTS, addressed this topic in a research article she co-authored with Dr. Mike Manhart on the effectiveness rates of FABMs to avoid pregnancy. Dr. Jenna Starke, a former FACTS elective participant, summarized the article titled, “Fertility awareness-based methods of family planning: A review of effectiveness for avoiding pregnancy using SORT.”[1] Dr. Starke highlights the need for more research and education about FABMs, which is one of the goals of the RESTORE Act, legislation introduced in the US Senate on June 13, 2024.

Introduction

With fertility awareness-based methods (FABMs) of family planning, a couple may seek to achieve or avoid pregnancy by timing intercourse to the woman’s fertile or infertile days. Most women are fertile up to five days before ovulation and one day after the egg is released, while most men are always fertile. [2] The hormonal changes throughout the female cycle can be observed or tracked using different biomarkers, leading to the four main types of FABMs that patients may choose: calendar-based methods, cervical fluid methods, sympto-thermal methods, and sympto-hormonal methods. The purpose of the study by Manhart et al [1] was to use the SORT criteria to assess the quality of effectiveness studies as well as unintended pregnancy outcomes, so medical professionals can incorporate this information into their practices.

“The hormonal changes throughout the female cycle can be observed or tracked using different biomarkers, leading to the four main types of FABMs that patients may choose: calendar-based methods, cervical fluid methods, sympto-thermal methods, and sympto-hormonal methods.”

Each FABM uses different biomarkers, has specific instructions for use, and must be analyzed based on its unique characteristics and effectiveness data. Below are some of the main differences and examples of each type of method:

• Calendar-based methods estimate fertility based on the day of the cycle. With the Standard Days Method (SDM), the woman’s cycle must be from 26 to 32 days long, and it is assumed she is fertile on days 8-19. [3]
• Cervical fluid methods track changes in cervical fluid or mucus throughout the cycle. Examples include the Billings Ovulation Method and the Creighton Model FertilityCare System. These methods assume fertility at the onset of secretions and / or sensation for 3 days after the last day of fertile type mucus.
• Sympto-thermal methods combine basal body temperature (BBT) with cervical mucus observations to predict fertility.
• Sympto-hormonal methods track urinary hormone metabolites and cervical mucus observations to determine fertility. Examples include the Marquette Model and FEMM.

Methodology

The researchers used the Strength of Recommendation Taxonomy (SORT) protocol to assess the quality of each study based on parameters relevant to family planning methods and FABMs. [4][5] Twelve different critical criteria were identified, such as appropriate sample size and at least one year of follow-up. Each study was given a score out of four points for each of the 12 criteria, which resulted in a grading scheme of up to 56 points. The literature search went as far back as 1980, and two authors scored each study separately.

Results

The search yielded 29 studies over a 32-year period, though only 11 studies had a SORT score >40 qualifying as a Level 1 or the highest quality study. Across all FABMs, with correct use of the method, there were 0.4-5 unintended pregnancies per 100 women years. With typical use, the effectiveness rates ranged from 2-14 unintended pregnancies per 100 women years based on Level 1 studies. These results are comparable to other behavioral methods of family planning, including hormonal birth control pills and barrier methods. [6][7]

“Across all FABMs … with typical use, the effectiveness rates ranged from 2-14 unintended pregnancies per 100 women years based on Level 1 studies.”

Discussion

The different types of FABMs provide various choices for women and couples seeking evidence-based, hormone-free family planning. Some FABMs can be taught in one visit while others require frequent follow up with a trained educator. Either way, these methods are cost effective and can be used throughout a woman’s reproductive life.

With only 29 studies identified over a 32-year period and 11 studies of high enough quality to be included in the review, it is clear more research is needed about FABMs. Additionally, though many assume FABMs are difficult to learn, studies show patients from a variety of backgrounds and literacy levels could successfully learn FABMs with limited time. [3][8][9]

“With only 29 studies identified over a 32-year period and 11 studies of high enough quality to be included in the review, it is clear more research is needed about FABMs.”

FABMs encourage couples to work together; they require communication and cooperation from each person. Similar to promoting behavior change to eat healthier meals or form healthy relationships, FABMs can be implemented while pursuing behavior change. These methods empower a woman to better understand her body, and some evidence suggests the quality of the couple’s relationship may also improve while using FABMs. [10]

Historically, the efficacy of FABMs with typical use has been improperly cited as 24 per 100 unintended pregnancies. [11] This is based on a survey that asked women to recall the form of contraception they were using when they became pregnant, and many of these women used self-devised versions of FABMs not formally taught and, thus, not equivalent to modern-day FABMs. More recent, evidenced-based studies have shown this is inaccurate, and this mistaken statistic should no longer be cited. [12][13]

Fertility awareness-based methods not only help women and couples postpone pregnancy but they can also help diagnose and treat the root cause of infertility and other gynecologic concerns. FABMs are an effective way to prevent pregnancy, understand a woman’s cycle and overall health, and they may also improve a couple’s communication. More research is needed on the efficacy of FABMs in different patient populations, and more education is needed for physicians around the use and effectiveness of FABMs.

References

[1] Manhart MD, Duane M, Lind A, et al. Fertility awareness-based methods of family planning: A review of effectiveness for avoiding pregnancy using SORT. Osteopathic Family Physician. 2013;5:2-8.
[2] Wilcox AJ, Weinberg CR, Baird DB. Timing of sexual intercourse in relation to ovulation. N Engl J Med. 1995;333(23):1517-1521.
[3] Arevalo M, Jennings V, Sinai I. Efficacy of a new method family planning: the Standard Days Method. Contraception. 2002;65:333-338.
[4] Ebell MH, Siewk J, Weiss BD, et al. Strength of Recommendation Taxonomy (SORT): a patient-centered approach to grading evidence in the medical literature. Am Fam Physician. 2004;69:548-556.
[5] Lamprecht V, Trussell J. Natural family planning effectiveness: evaluating published reports. Adv Contracept. 1997;13(2/3):155-165.
[6] Trussell J. Contraceptive failure in the United States. Contraception. 2011;83:397-404.
[7] Winner B, Peipert JF, Zhao Q, et al. Effectiveness of long-acting reversible contraception. N Engl J Med. 2012;366(21):1998-2006.
[8] Field trial of billings ovulation method of natural family planning. Contraception. 1996;53(2):69-74.
[9] Arevalo M, Jennings V, Nikula M. Efficacy of the new Two Day Method of family planning. Fert Ster. 2004;82:885-892.
[10] Pallone SR, Bergus GR. Fertility awareness-based methods: another option for family planning. J Am Board Fam Med. 2009;22:147-157.
[11] Hatcher, RA, Trussell J, Nelson AL. Contraceptive Technology. 19th Revised ed. Ardent Media. 2009 759.
[12] Duane M, Stanford JB, Porucznik CA, et al. Fertility awareness-based methods for women’s health and family planning. Front Med (Lausanne). 2022;9:858977.
[13] Duane M, Motley R, Manhart M. Physicians need more education about natural family planning. Am Fam Physician. 2013 Aug 1;88(3):158-9. PMID: 23939690

ABOUT THE AUTHOR

Jenna Starke, MD

Jenna Starke, MD is a first-year resident at the North Colorado Family Medicine Residency in Greeley, CO. She earned her medical degree at the University of Washington School of Medicine with the regional Montana WWAMI program in Bozeman, MT, and completed her undergraduate education at Carroll College in Helena, MT. She is interested in full spectrum, rural family medicine with obstetrics. She enrolled in the FACTS elective to gain a better understanding of natural family planning methods and to learn how to share these methods with patients so they feel more empowered about their health and reproductive decisions.