Sex & Theology of the Body

From Humanae Vitae: Faithfulness to God's Design means to experience married love while respecting the laws of conception and to acknowledge that one is not the master of the sources of life but rather the minister of the design established by the Creator. All artificial birth control methods are unlawful as are all specifically intended to prevent procreation—whether as an end or as a means. Lawful Therapeutic Means are permitted if necessary to cure bodily diseases, even if a foreseeable impediment to procreation should result, provided such impediment is not directly intended for any motive whatsoever. Recourse to Infertile Periods applies to the spacing of births, arising from the physical or psychological condition of the husband or wife, or from external circumstances. The Church teaches that married people may then take advantage of the natural cycle. Scientists, as already requested by Pius XII, should study natural rhythms as a secure basis for the limitation of offspring.