Fertility Awareness-Based Methods: Another Option for Family Planning

Stephen R. Pallone, MD; George R. Bergus, MD


J Am Board Fam Med. 2009;22(2):147-157. 

In This Article


There has been considerable debate about the soundness of the research on FABMs' effectiveness. Some research methods make comparison between FABMs and other contraceptive methods difficult. There are few randomized controlled studies of FABMs; existing randomized trials were judged to be of insufficient quality to draw any valid conclusions.[44] Many recent studies of modern FABMs included only self-selected patients, which is more consistent with clinical practice.[5,11] Early FABM investigations usually excluded data from the "learning phase" (typically 3 cycles), skewing the data in favor of FABMs. More recent studies include this period in their data.[5,11]

In addition, FABMs are unique in that they can also be used for achieving pregnancy. Pregnancy rates are therefore reported in categories of perfect-use (method-related) pregnancies, achieving-related pregnancies, and typical-use pregnancies. The achieving category allows for the proper classification of women who change their minds mid-cycle about wanting to avoid pregnancy; they would be labeled as typical-use pregnancies in contraceptive trials that categorize women based on their decision to avoid pregnancy at the beginning of each cycle. On the other hand, the achieving category includes women who engage in coitus at a time when they know they are fertile even if their intention is to avoid pregnancy. Recent FABM studies typically report all 3 of these categories, with some variation in the achieving-related category. The 2 most useful for comparison are the perfect-use and typical-use pregnancy rates.

There have been attempts to characterize women who are successful (likely to persist in using the methods as described) with FABMs; however, no consistent positive predictors across studies have been found.[45,46] Successful use is probably determined in part by societal attitudes regarding sexual behavior and sexuality, religious beliefs, and personal characteristics of the woman choosing to use them, such as interest in alternative medicine and the support of her partner. Most studies of FABMs included predominantly women who are in long-term and stable relationships. Most users of FABMs in US studies have been Roman Catholic, in a long-standing committed relationship, white, have a high school education or higher and a gross income more than $20,000 per year.[9,46] Although uncommonly used in the United States, as many as 20% of married women in other countries use one of these methods.[47]

The lowest pregnancy rates associated with FABMs are achieved by women who choose to use these methods and have been properly instructed in how to do so. International studies suggest poverty-stricken populations have lower rates of typical-use pregnancy when using FABMs, in some cases approaching 0%.[5,12] Poverty may be a significant motivator for successful FABM use because the cost of raising a child is high and access to conventional contraceptives is limited.[48] However, studies in the United Kingdom, Italy, and Germany report similarly low rates of pregnancy,[13,14,15,16] even in younger unmarried populations.[19] Some international studies have also included women of diverse religions (including Hindus, Muslims, and Buddhists); races; and socioeconomic status. The success of these other demographic groups coupled with insufficient knowledge about FABMs in the medical community in the United States suggests American white, upper-middle class, and Catholic women are more likely to use FABMs in part because they have more access to information about these methods.[48] Lack of support from the husband and physical separation of the partners are thought to be predictors of FABM failure or discontinuation.[17] Reasons for discontinuation of some FABMs are summarized in Table 3.

All FABMs are physiologically compatible with the use of barrier methods. Use of barriers during fertile periods reduces the overall undesired pregnancy rate with typical use of the Standard Days and TwoDays methods but also increases perfect-use pregnancies.[10,21] Conversely, studies examining symptothermal methods have shown no significant differences in method- and typical-use pregnancies with or without use of barriers while still maintaining low unintended pregnancy rates.[19,20,49] NFP methods stress that the use of barriers is abandonment of the method.[26,50,51]


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