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 systems are known as the Knaus–Ogino Method, rhythm method, and Standard Days Method. These systems may be used to achieve pregnancy by timing unprotected intercourse for days identified as fertile, or to avoid pregnancy by restricting unprotected intercourse to days identified as infert...
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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 systems are known as the Knaus–Ogino Method, rhythm method, and Standard Days Method. These systems may be used to achieve pregnancy by timing unprotected intercourse for days identified as fertile, or to avoid pregnancy by restricting unprotected intercourse to days identified as infertile.
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 1999, when Georgetown University...
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