Natural family planning (NFP) is a method used by couples to achieve or avoid pregnancy by observing and tracking the natural signs of fertility in a woman's menstrual cycle. This includes monitoring changes in body temperature, cervical mucus, and menstrual cycle patterns to identify fertile and infertile days. NFP does not involve the use of artificial contraceptives or hormonal treatments. Instead, it relies on understanding the body's natural rhythms and can be used in conjunction with other methods, such as the calendar method or symptothermal method, to enhance effectiveness.