Some natural birth control methods, known as “fertility awareness methods,” do not rely on medicaments or mechanical devices. One such natural method has been used for centuries; the “rhythm method,” sometimes called the “calendar method,” is the avoidance of sexual intercourse during periods of high fertility. This method does not harm the health of the practitioner and has no long-term effects on fertility.
Regular Fertility Cycles
Fertility normally waxes and wanes in women of childbearing age, coincidentally paralleling to a rough degree the cycles of the moon. The relevant biological function is ovulation, which is the regular monthly release of one (or more) mature egg from one of the ovaries into the fallopian tubes. Pregnancy results when an egg is fertilized by sperm from a male sexual partner. The monthly onset of menstruation marks the shedding of the uterine lining if no pregnancy has occurred.
Timing Menstrual Rhythms
The rhythm method aims to prevent sperm from meeting unfertilized eggs, which requires predicting when the eggs will be released. Proper implementation of the rhythm method begins with charting every day of each menstrual cycle for a minimum of two months, although six months is preferable. A normal menstrual cycle, which starts on the first day of bleeding and ends on the first day of next menstrual cycle, may range in duration from 23 to 35 days; however, 28 to 29 days is typical for most women. After collecting this base information, peak probabilities for ovulation may be calculated.
Calculating Likely Ovulations
Usually, ovulation will occur 14 days before the beginning of a new menstrual cycle (next period). Thus, if a full cycle has been observed as 28 days, then ovulation is predicted to take place on 14th day of the next cycle. This is calculated by subtracting 14 days from 28 days, which equals to 14 days. In this case, it means that days 12-16 of the menstrual cycle represent most fertile days and the 14th day has peak fertility (theoretically). Sexual intercourse should be avoided on these days; some women may choose instead to resort to a barrier method.
Another example: If a full cycle has been observed as 32 days, then ovulation is predicted to take place on 18th day (32-14=18) of the menstrual cycle. Here, the most fertile days are around 16th-20th. The fertile days can slightly move either way.
At first, these simple calculations and predictions may seem confusing; an individual considering this method should clarify comprehension by discussing the matter with a skilled caregiver.
Caveats and Considerations
Because it does not take into account individual biological variability, the rhythm method is not as reliable as other methods. Performed flawlessly, this method will result in a pregnancy rate of 1 to 9 percent; a more typical rate for most people will be 25 percent. The rhythm method does not offer any protection against sexually transmitted diseases.
Mature sexual partners might very well be more closely drawn together emotionally by the mutual effort of monitoring and responding to peak fertility. The rhythm method probably is not suitable for teenagers, however, because of the self-discipline required of participants.