Natural Family Planning (NFP) is the general title for the scientific, natural, and moral methods of family planning that can help married couples either achieve or postpone pregnancies.
NFP methods are based on the observation of the naturally occurring signs and symptoms of the fertile and infertile phases of a woman’s menstrual cycle. No drugs, devices, or surgical procedures are used to avoid pregnancy.
Since the methods of NFP respect the love-giving (unitive) and life-giving (procreative) nature of the conjugal act, they support God’s design for married love! (USCCB)