69 Those who act in this way are at fault in losing sight of the fact that the family is more sacred than the State and that men are begotten not for the earth and for time, but for Heaven and eternity. Although often these individuals are to be dissuaded from entering into matrimony, certainly it is wrong to brand men with the stigma of crime because they contract marriage, on the ground that, despite the fact that they are in every respect capable of matrimony, they will give birth only to defective children, even though they use all care and diligence.
Source: Casti Connubii (Vatican.va)