Back in high school biology class, you were probably taught that ovulation occurs 14 days before your next menstrual bleeding. This fact, when it was discovered in the 1920s, gave rise to the Calendar or Rhythm method of fertility awareness. It is the oldest recorded and most widely practiced method of natural family planning and in the early in the twentieth century, the Catholic Church proclaimed the rhythm method as the only morally acceptable form of family planning.
At one time the Calendar-Rhythm Method was synonymous with natural family planning. Today however, we know that the much vaunted 14th day of the cycle is not actually a hard fact. Each women's ovulation date is different, and therefore this method is not very accurate. There are many other natural contraceptive methods which are also now accepted by the Catholic Church.
The Three Keys to the Calendar Method
The Calendar Method is based on three assumptions:
- 1. That ovulation occurs fourteen days before the beginning of menstruation, (plus or minus two days)
- 2. That sperm remain alive for three days, and
- 3. That the ovum (egg) survives for twenty-four hours.
To practice this method, a woman with regular cycle needs to count backwards from the first day of her period in order to identify the day of ovulation, which is usually the fourteenth day from the first day of her period. With this information, a woman was able to predict when ovulation will occur the following month and then abstain from intercourse during that time to avoid pregnancy.
Efficiency of the Calendar Method
Uh Oh - most women do not ovulate at the same time every month, and no woman's cycles are identical each time. Because of this, the calendar method is not very effective. For women with very regular cycles, the failure rate is probably close to 13% and that is for the few who actually ovulate on the 14th day. This method is completely ineffective if used improperly. So for most women, there is very little to no insurance when using this method.
This method is rarely even taught as new methods have been proven to be more effective. If you are interested in using this type of method, consider the standard days method instead, which is easier and more effective. Or check out the Sympto-Thermal method. This method allows you to pinpoint your exact date of fertility and offers 99% contraceptive reliability and with the use of a contraceptive monitor like Cyclotest, it is surprisingly uncomplicated.