From Pope St. John Paul II’s Apostolic Exhortation Familiaris Consortio (1981):
With regard to the question of lawful birth regulation, the ecclesial community at the present time must take on the task of instilling conviction and offering practical help to those who wish to live out their parenthood in a truly responsible way.
In this matter, while the Church notes with satisfaction the results achieved by scientific research aimed at a more precise knowledge of the rhythms of women’s fertility, and while it encourages a more decisive and wide-ranging extension of that research, it cannot fail to call with renewed vigor on the responsibility of all—doctors, experts, marriage counselors, teachers and married couples—who can actually help married people to live their love with respect for the structure and finalities of the conjugal act which expresses that love. This implies a broader, more decisive and more systematic effort to make the natural methods of regulating fertility known, respected and applied.97
A very valuable witness can and should be given by those husbands and wives who through the joint exercise of periodic continence have reached a more mature personal responsibility with regard to love and life. As Paul VI wrote: “To them the Lord entrusts the task of making visible to people the holiness and sweetness of the law which unites the mutual love of husband and wife with their cooperation with the love of God, the author of human life.”98
97 Cf. John Paul II, Address to the Delegates of the Centre de Liaison des Equipes de Recherche (Nov. 3, 1979), 9: Insegnamenti, II, 2 (1979), 1035; and cf. Address to the Participants in the First Congress for the Family of Africa and Europe (Jan. 15, 1981): L’Osservatore Romano, Jan. 16, 1981.
98 Encyclical Humanæ Vitæ, 25: Acta Apostolicæ Sedis 60 (1968), 499.
— Familiaris Consortio 35