'Fertility awareness-based methods' of family planning "involve identification of the fertile days of the menstrual cycle, whether by observing fertility signs such as cervical secretions and basal body temperature, or by monitoring cycle days. Fertility awareness-based methods can be used in combination with abstinence or barrier methods during the fertile time" (WHO 2000). Several names have been used to describe this approach to contraception, including 'rhythm,' 'natural family planning' and 'periodic abstinence.' Fertility awareness-based methods can be used with abstinence from sexual intercourse. Alternatively, they can be used with barrier contraceptives or withdrawal during presumed fertile times.