The true nature of marriage, a husband and wife living in openness to life, is also a witness to the precious gift of the child and to the unique and irreplaceable roles of both a mother and a father. In creating new life, the unitive and procreative purposes of marriage come together. Marriage, therefore, is not confined wholly to the loving intimacy of husband and wife but strives in generosity to go beyond this to bring new life into being.
This procreative meaning of marriage involves not only the conception of children but also their upbringing and education. The loving communion of marital spouses is the primary context in which children are both conceived and brought up in love.
It is true that some marriages will not result in procreation due to infertility, even though the couple is capable of the natural act by which procreation takes place. Indeed, this situation often comes as a surprise and can be a source of deep sadness, disappointment, anxiety, and even great suffering for a husband and wife.
When such tragedy affects a marriage, a couple may be tempted to think that their union is not complete or truly blessed. This is not true. The marital union of a man and a woman is a distinctive communion of persons which even infertile couples continue to manifest.