NFP or Natural Family Planning is a natural way of increasing or decreasing possibility of pregnancy. It is based on the body’s built-in system of fertility. Properly done, it is 97-98% effective, natural, and open to the important aspects of Christian unitive and procreative love. In contrast, contraceptive approaches to limit the possibility of pregnancy are often much less effective, are unnatural, and are not open to the fullest expression of love.
How does it work? Women have natural cycles of fertility that can be precisely measured with today’s technology in a way that was not possible even 20 to 30 years ago. During the fertile days of the cycle (a little over a week) the couple either abstains (to limit pregnancy) or partakes in love making (to increase the probability of pregnancy). More information on the theology and the methods can be found below:
https://pastoralministry.archdpdx.org/natural-family-planning