TO THE EDITOR: From a patient-centered perspective, there is enough interest in natural family planning (NFP) to consider it as an option for family planning and gynecologic health. However, the authors of the article state that only one-half of physicians would provide information about NFP to patients who wish to prevent pregnancy. Our survey of 120 family medicine residency programs found that more than one-half of women's health faculty members were not familiar with modern methods of NFP, and 25% of these programs do not include NFP in the women's health curriculum.¹ This knowledge gap among family physicians is a barrier to providing accurate information and referral for interested patients.

The authors cite a 76% user-effectiveness rating for NFP. This widely quoted figure, which perpetuates the knowledge gap, is derived from surveys of women with unintended pregnancies who were asked which family planning method they were using at the time of conception.² From this number, all NFP methods are pooled, then adjusted to account for underreporting of abortion, and an estimated unintended pregnancy rate is generated. Fully 86% of NFP users surveyed identified the calendar rhythm method—a much older and less effective method—as their primary form of contraception.³ This lumping together of NFP methods masks important differences in their effectiveness, a fact acknowledged by the author of this estimate.⁴

We recently used the Strength of Recommendation Taxonomy to review NFP studies published in peer-reviewed journals since 1980.⁵ We found that with typical use, the effectiveness of individual NFP methods ranged from 85.8% to 98.4%, based on good-quality studies.

The principles for effective use of NFP are similar to those for self-management for diabetes mellitus and smoking cessation. Successful patients are motivated and receive adequate instruction and physician support. We know from NFP model-specific data that among well-instructed, motivated couples, NFP effectiveness rates are comparable with those of generally accepted methods of contraception.

Choosing a family planning method is an important decision. We can best serve our patients who are interested in NFP by becoming more familiar with the evolving body of literature and guiding appropriately selected, interested patients toward resources that facilitate effective use.

IN REPLY: We thank Drs. Duane, Motley, and Manhart for their insightful comments. They have highlighted important caveats in the interpretation of the National Survey of Family Growth (NSFG) statistics about NFP. However, these results do not necessarily need to be viewed as perpetuating a knowledge gap. Instead, the use of the outdated calendar rhythm method by NSFG interviewees is evidence of the need to close a knowledge gap about modern NFP methods. Additionally, the reported typical-use effectiveness of 76% is based on data from 1995 and 2002 surveys.¹ The age of these results demonstrates the need for an updated analysis that would assess the typical-use effectiveness of specific NFP methods rather than lumping them together. In the meantime, data about perfect use support their conclusion that we can best serve appropriately selected, interested patients by guiding them toward resources that will facilitate effective use.