Choosing a Birth Control Method – Fertility Awareness

(Updated June 2014)


A variety of contraceptive methods known variously as fertility awareness, natural family planning, rhythm, and other names may be suitable choices for couples who are highly motivated to abstain from vaginal intercourse or who use a barrier method during “fertile” days.

All fertility awareness methods are based on identifying the fertile days in a woman’s menstrual cycle by counting the days in the menstrual cycle and/or noting changes in fertile signs such as cervical mucus and basal body temperature (BBT). On days identified as fertile, the couple either abstains from vaginal intercourse or uses a barrier method.

fertility awareness cycle beadsBecause these methods are based on the woman’s ovulatory cycle, they are most effective for women who have reliably regular menstrual periods, between 26 and 32 days in length. Women who have two or more periods differing from this length within a single calendar year are not good candidates for these methods.


In the Standard Days Method®, the days of the menstrual cycle are tracked on a calendar. Day 1 is the first day of menstruation and days 8 through 19 are the fertile days, when unprotected intercourse is avoided. A product called Cycle Beads™ ( is a simple visual aid to help a woman keep track of her cycle days and fertile period.

In the Calendar Days Method, a woman keeps track of her menstrual cycle for 6–12 months and then subtracts 18 from the number of days in the shortest cycle and 11 from the number of days in the longest cycle. The two resulting numbers indicate the beginning and end of the fertile period. The ovulation method involves tracking changes in cervical mucus and/or BBT daily to determine fertile and non-fertile days. Cervical mucus changes in amount and texture around the time of ovulation, and BBT, which is measured every morning, rises by about 0.4° F around the time of ovulation. Alternatively, women can monitor the timing of ovulation using ovulation kits, which are available without prescription at pharmacies. Downloadable calendars are available at

The TwoDay Method® requires women to monitor for cervical secretions every day. On any day when the woman observes secretions—or observed them the previous day—she considers herself to be fertile and avoids intercourse. When she notes 2 consecutive days without cervical secretions, she is unlikely to become pregnant from intercourse on that day.94

For some women, libido is high during fertile days, making abstinence an undesirable practice. Other couples find that intimacy is enhanced by practicing non-penile-vaginal forms of sexual expression during the fertile period.


  • This method is somewhat effective. With correct and consistent use of fertility awareness–based methods, the failure rate is 0.4 to 5 percent.19 With typical use, the failure rate is as high as 24 percent.19
  • To be effective, this method requires highly motivated couples where the woman has a reliably regular menstrual period.



Side Effects


Contraindications and Precautions



  • Low or no cost
  • Readily available once trained in method
  • Also can be used to pinpoint fertile days in order to conceive


  • Requires cooperation of male partner
  • Lower efficacy than other methods with typical use
  • Lack of spontaneity on fertile days
  • Unsuitable for women with cycles of fewer than 26 or more than 32 days in length
  • No protection against STIs

Counseling Messages

  • Correct use of fertility awareness methods is important for these methods to be used successfully.
  • The Standard Days Method can be learned quickly and easily, whereas the ovulation method requires more practice and training for patients to accurately recognize changes in cervical mucus.
  • This method does not protect against STIs.