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Rhythm Method (1930's)
 The Rhythm Method was developed independently in the late 1920's by Knauss in Germany, and Ogino in Japan. It was used successfully during the 1930's. For women with regular cycles it can be up to 85 percent effective in postponing a pregnancy. As is the case with all natural methods, it requires that a couple abstain from sexual contact during the fertile time.
The method is based on the fact that a woman is fertile for 5 to 8 days, ending about 11 days before the onset of the next menstruation. To make use of this method it is presumed that a woman's cycle will not deviate appreciably from the preceding six to twelve cycles.
The couple will subtract 19 (=11+8) days from the shortest cycle to find the first fertile day. They will subtract 11 days from the longest cycle to find the last fertile day of this cycle. As an example, if cycles range from 27 to 29 days, the first fertile day will be 8 (=27-19) while the last fertile day will be day 18 (=29-11), requiring abstinence for 11 days.
To improve the success rate, variations were proposed, for example 19 and 11 were changed to 21 and 9 respectively, changing the calculated fertile time to days 6 through 19, which requires more than two weeks of abstinence, sometimes resulting in less effectiveness.
Sample chart of the Rhythm Method
In the 1990's and 2000's we know of four Rhythm Methods, which some women, especially those with a family history of regular cycles, use with success. They like the simplicity. A new version of this method, called "The Standard Days Method" was published in 2002. It uses a string of "cycle beads" to record cycle days.
This method is not taught by the Archdiocese of Detroit, nor are any of the many simple temperature methods. The OM and STM, with success rates of 99 percent, however, are taught regularly.
Temperature Method
In the 1940's, the Strict Temperature Method, with a success rate of 99%, was proposed as an improvement over the Rhythm Method.
 It is based on the fact that a woman's basal body temperature (temperature at rest) rises about 0.75 F around the time of ovulation and falls again at the next menstruation. After day two of the sustained temperature rise, pregnancy does not occur. Therefore, to postpone a pregnancy, a couple abstains starting at the beginning of menstruation until the temperature rise. Proposed ways of reducing the duration of abstinence are all based on some variation of Rhythm. The couple can then express their conjugal love at the beginning of the cycle, with a reduction in effectiveness. The most common methods subtract a number such as 19, 20, or 21 from the shortest previous cycle to find the first possibly fertile day. Others subtract a number such as 7, 8 or 9 from the earliest day of temperature rise in previous cycles. Digital thermometers are used.
Sample Chart of Temperature Method
This method is not taught by the Archdiocese of Detroit, nor is the Rhythm Method. The OM and STM, with success rates of 99%, however, are taught regularly. | 
