rhythm method

     

Calenar-based methods are various methods of estimating a female human'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.

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