Natural Family Planning (NFP) is an umbrella term for certain methods used to achieve and avoid pregnancies. These methods are based on observation of the naturally occurring signs and symptoms of the fertile and infertile phases of a woman’s menstrual cycle.
NFP is not “Rhythm.” The Rhythm (or Calendar) method was developed in the 1930s. It was based on the scientific theory that ovulation could be predicted by calculating previous menstrual cycles. This method was often inaccurate because it did not take account of the unique nature of each woman’s menstrual cycles.