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

Calendar Methods

The Rhythm Method (RM), introduced in the 1920s before the availability of hormonal methods of contraception, was the first FABM. At its inception, it was believed to be one of the most effective methods of birth control.[4,59] The effectiveness of RM has never been precisely determined. The few existing RM studies used different rules about when not to have intercourse or did not report these rules.[59] Studies of RM often included individuals who reported using intercourse rules inconsistent with any validated calendar method.[45,60] It is not clear whether this misuse of the method came from a lack of formal information, lack of proper instruction, or whether the instructions were difficult to understand.

One type of traditional RM is practiced by counting days in a cycle, with the beginning of menstruation being day 1 for each cycle. Days 12 to 19 (inclusive) are considered fertile. The difference between the longest and shortest of the previous 8 to 12 cycles are subsequently added as additional fertile days at the beginning of the fertile time. This method was initially reported to be so effective that there were no pregnancies for more than 54,000 acts of coitus when the method was used properly.[61,62] A meta-analysis later reported total unplanned pregnancy rates of 15% to 18.3%.[59]

Effective use of the RM is hindered by events that affect the length and regularity of the menstrual cycle, including the use of hormonal contraceptives, recent pregnancies or childbirth, breastfeeding, menarche or menopause, inherent cycle variation, or illness. More pregnancies result when cycles are irregular. RM typically overestimates the fertile period, and accurate history of the menstrual cycles of the previous 8 to 12 months is necessary for use of the method. Without data about past cycles it is not considered reliable for avoiding pregnancy.[62]

One modern user-friendly calendar method is the SDM. It is applicable for women with cycles consistently between 26 and 32 days (inclusive). It differs from previous calendar methods in that historical data are not needed to calculate the fertile window. Days 8 to 19 (inclusive) are considered fertile for all users of this method. Two or more cycles outside of the 26- to 32-day range within 1 year contraindicate SDM use, which excluded 28% of the original sample from further participation in the study.[21] Color-coded cycle beads, essential to SDM practice, help with tracking fertile and infertile days and are available for $12 per a kit, including instructions. Use of SDM is also limited during variable menstrual cycles.[21]


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