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Calendar-based methods are various methods of estimating a woman's likelihood of fertility, based on a record of the length of previous menstrual cycles. Various methods are known as the Knaus–Ogino Method and the Rhythm Method. The Standard Days Method is also considered a calendar-based method, because when using it, a woman tracks the days of her menstrual cycle without observing her physical fertility signs. The Standard Days Method is based on a fixed formula taking into consideration the timing of ovulation, the functional life of the sperm and the ovum, and the resulting likelihood of pregnancy on particular days of the menstrual cycle. These methods may be used to achieve pregnancy by timing unprotected intercourse for days identified as fertile, or to avoid pregnancy by avoiding unprotected intercourse during fertile days. The first formalized calendar-based method was developed in 1930 by John Smulders, a Roman Catholic physician from the Netherlands. It was based on knowledge of the menstrual cycle. This method was independently discovered by Hermann Knaus (Austria), and Kyusaku Ogino (Japan). This system was a main form of birth control available to Catholic couples for several decades, until the popularization of symptoms-based fertility awareness methods. A new development in calendar-based methods occurred in 2002, when Georgetown University introduced the Standard Days Method. The Standard Days Method is promoted in conjunction with a product called CycleBeads, a ring of colored beads which are meant to help the user keep track of her fertile and non-fertile days. ==Terminology== Some sources may treat the terms ''rhythm method'' and ''fertility awareness'' as synonymous. However, fertility awareness is usually used as a broad term that includes tracking basal body temperature and cervical mucus as well as cycle length. The World Health Organization considers the rhythm method to be a specific type of calendar-based method, and calendar-based methods to be only one form of fertility awareness. More effective than calendar-based methods, systems of fertility awareness that track basal body temperature, cervical mucus, or both, are known as symptoms-based methods. Teachers of symptoms-based methods take care to distance their systems from the poor reputation of the rhythm method. Many consider the rhythm method to have been obsolete for at least 20 years, and some even exclude calendar-based methods from their definition of fertility awareness. Some sources may treat the terms ''rhythm method'' and ''natural family planning'' as synonymous. In the early 20th century, the calendar-based method known as the ''rhythm method'' was promoted by members of the Roman Catholic Church as the only morally acceptable form of family planning. Methods accepted by this church are referred to as natural family planning (NFP): so at one time, the term "the rhythm method" was synonymous with NFP. Today, NFP is an umbrella term that includes symptoms-based fertility awareness methods and the lactational amenorrhea method as well as calendar-based methods such as rhythm. This overlap between uses of the terms "the rhythm method" and "natural family planning" may contribute to confusion. The term "the rhythm method" is sometimes used, in error, to describe the behavior of any people who have unprotected vaginal intercourse, yet wish to avoid pregnancy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Calendar-based contraceptive methods」の詳細全文を読む スポンサード リンク
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