The fecundity of marriage
The state has a responsibility for its citizens' well-being. In this capacity it is legitimate for it to intervene to orient the demography of the population. This can be done by means of objective and respectful information, but certainly not by authoritarian, coercive measures. The state may not legitimately usurp the initiative of spouses, who have the primary responsibility for the procreation and education of their children. It is not authorized to intervene in this area with means contrary to the moral law.
Source: Catechism of the Catholic Church (Vatican.va)