What reasons justify avoiding pregnancy?

Left to the couple

The Catechism says that, for just reasons, spouses may wish to space their children's births, but it does not define those reasons. The couple must make sure their desire comes not from selfishness but from the generosity proper to responsible parenthood (CCC 2368).

What Church documents say

• Gaudium et Spes (51) notes that modern conditions can put couples in situations where, at least for a time, their family should not grow.
• Humanae Vitae (16) says couples may morally space births for well-grounded reasons arising from the physical or psychological condition of husband or wife, or from external circumstances.
• The Vademecum for Confessors Concerning Some Aspects of the Morality of Conjugal Life (2.3) says married couples, seeking suitable counsel, have a duty to deliberate deeply and in faith about the size of their family and how to realize it, respecting the moral criteria of married life.

How to judge

Gaudium et Spes (50) teaches that parents are cooperators with, and interpreters of, the love of God the Creator in handing on and educating life. They should decide together, with reverence toward God, weighing their own welfare and that of their children, born and yet to come, the material and spiritual conditions of the times and of their state in life, and the interests of the family, society and the Church. The parents themselves, and no one else, must make this judgment before God. But they cannot act arbitrarily: they must follow a conscience formed by God's law and be docile to the Church's teaching office, which interprets that law in the light of the gospel.