Fertility awareness-based methods (FABM), or natural family planning (NFP), is one of the oldest practiced methods of birth control. Also known by the name’s periodic abstinence, rhythm method, standard days method, and the two-day method, it can be used for either pregnancy prevention or planning and is acceptable to all major religious groups. Fertility awareness-based methods are based on the observation of fertile and infertile periods of the menstrual cycle. Each of the various methods relies on the identification of cervical mucus changes, a change in basal body temperature that increases around the time of ovulation, and/or a change in the position and feel of the cervix. There are also commercially available fertility monitoring devices and numerous Internet apps that can be used to assist the couple.