37. There is no denying that the accelerated rate of population growth brings many added difficulties to the problems of development where the size of the population grows more rapidly than the quantity of available resources to such a degree that things seem to have reached an impasse. In such circumstances people are inclined to apply drastic remedies to reduce the birth rate.
There is no doubt that public authorities can intervene in this matter, within the bounds of their competence. They can instruct citizens on this subject and adopt appropriate measures, so long as these are in conformity with the dictates of the moral law and the rightful freedom of married couples is preserved completely intact. When the inalienable right of marriage and of procreation is taken away, so is human dignity.
Finally, it is for parents to take a thorough look at the matter and decide upon the number of their children. This is an obligation they take upon themselves, before their children already born, and before the community to which they belong - following the dictates of their own consciences informed by God's law authentically interpreted, and bolstered by their trust in Him. (Ibid., nos. 50-51, with note 14: AAS 58 (1966), 1070-1073 [cf. TPS XI, 292-293]; also no. 87, p. 1110 [cf. TPS XI, 319-320])