"The transmission of human life is a most serious role in which married people collaborate freely and responsibly with God the Creator. It has always been a source of great joy to them, even though it sometimes entails many difficulties and hardships." Humanae Vitae n.1
A fundamental knowledge of the Church teachings regarding the fruitfulness of the married love and the regulation of births is essential in order to live faithfully the vocation to marriage. After all marriage is an institution established by God to protect two great human goods, two goods intimately connected; the love between a male and a female, and the good of the human life that comes from that love. Thus the two deeply inter-related purposes of sexuality in marriage (strengthening the mutual bond of husband and wife and Procreation of children) can only be fulfilled by understanding and embracing Natural Family Planning.