Natural family planning (NFP) is an effective and fulfilling method of avoiding pregnancy ¹ that has developed significantly over the past 80 years. Because many physicians lack a correct understanding of modern NFP methods, they may underestimate the effectiveness of NFP and offer limited information to their patients.^2–4 Between 40 and 60 percent of surveyed women report that they are interested in learning more from their physicians about nonhormonal, nonbarrier, and nonsurgical methods of birth control.^5–7 This interest reaches across geographic regions, religions, and socioeconomic and education levels.^7,8

Only 1 to 3 percent of U.S. women use NFP for birth control.⁸ Although most women included in studies of NFP are in stable long-term relationships and have high educational levels and socioeconomic status, there are no proven predictors of success.⁸ International studies have demonstrated the effectiveness of NFP, regardless of the user's religion, marital status, or socioeconomic level.⁸ A survey of women who use NFP indicated that less than 1 percent made the decision to use it based on the advice of their physician.⁸

NFP practices are thought to be complicated, but actually can be simple. For example, a woman using the TwoDay Method asks herself, “Did I note cervical secretions today?” and “Did I note cervical secretions yesterday?” If the answer to either question is “yes,” she is considered fertile. If the answer to both is “no,” her probability of conceiving that day is low.⁹ This method can be taught within the time allowed for a contraceptive counseling visit.⁸ Significant advantages of this method include its effectiveness, regardless of cycle regularity or irregularity.^9,10

With correct use, the failure rate of NFP is similar to those of more commonly accepted hormonal and barrier contraceptive methods. The symptothermal method, which monitors basal body temperature, cervical secretions, cervical position, and cycle patterns to predict periods of fertility, has been proven effective: its failure rate is 0.4 percent per year with perfect use, and 7.5 percent per year with typical use.¹ The effectiveness of the TwoDay method rivals that of condoms: with perfect use, the TwoDay Method has a 4 percent annual rate of unintended pregnancy compared with 2 percent for condoms; with typical use, 14 percent compared with 18 percent for condoms.¹⁰

NFP is effective and offers benefits that hormonal and barrier contraceptive methods cannot, including no or low cost, ease of use, no systemic adverse effects, and no medication interactions.^4,5,10 NFP is safe for women in whom hormonal methods are undesirable because of medical comorbidities. NFP empowers the couple in understanding fertility, increases relationship satisfaction, and is associated with lower rates of elective termination.^4,5,8 More than 90 percent of TwoDay users and their partners report being satisfied with this method.^5,10 Some physicians may avoid recommending NFP because they think periodic abstinence will interfere with a couple's sex life; however, couples who use NFP have equal or more frequent sex compared with non-NFP users.⁸ Additionally, knowledge of fertility awareness can help a couple conceive effectively, without the delay in return to fertility that occurs with some artificial contraceptive methods.⁸ To make NFP methods easier to follow, computer programs are available that help a woman track her daily symptoms and fertile days.¹¹

As noted in a 2004 Cochrane review, a systematic review of the evidence for NFP is challenging.¹² Because of the lack of consistency among available randomized controlled trials, a meta-analysis combining data from multiple studies could not be performed. Despite these challenges, there are numerous studies on NFP methods that are promising and noteworthy. NFP should be included in birth control counseling because it can be used effectively if the couple commits to it. Modern NFP methods are as effective as hormonal and barrier contraception, and family physicians should understand and discuss these methods with their patients.^3,8