Responsible parenthood concerns the consideration of the factors or conditions, which have a bearing on family size. When considering physical, economic, psychological and sociological factors, couples are responsible to God, to themselves, to their families and to society, in that order. Natural Family Planning assists couples in making generous and responsible decisions regarding family size.

NFP is personalized. Every woman learns how to understand her own body and its cycles, through one or more simple biological signs. With her husband, the two of them discuss and record their observations, gaining an awareness of and new appreciation for their shared fertility. If a couple wants to conceive, they have intercourse on fertile days. If they need to postpone pregnancy, they wait until the infertile times. The average woman is fertile from 8-12 days a month.

Responsible parenthood involves self-mastery and an understanding, as well as a proper ordering, of one’s drives or passions. Natural Family Planning fosters self-control and helps couples accept more fully the responsibility God gives with regard to procreation.

Catholic Church teaching does not say that a couple must intend to have a child in each and every marriage act. Should intercourse take place during the fertile time, when conception is possible, the couple must respect this possibility and must not frustrate it through contraceptive measures. The life-giving potential of the marital act must not be deliberately removed. With the use of Natural Family Planning, unlike contraception, nothing is done before, during or after the martial act to render the act sterile, incomplete or to prevent implantation of a fertilized ovum.