The book of Tobit in the Bible has a very interesting reference on the matter.
Sarah has had 7 husbands and all died at the time of intercourse with her. Finally, Tobiah decides to marry Sarah and before they have intercourse on their wedding night, they get up and pray to God a beautiful prayer.

“Now, Lord, you know that I take this wife of mine not because of lust, but for a noble purpose. Call down your mercy on me and on her, and allow us to live together to a happy old age.” Tobit 8:5-7.

They then have intercourse and live.  It is beautiful what happens when we ask for and receive God's blessing before we act.

In sexual intercourse, our body is involved of course, but we must also involve our soul and heart. We are meant to be WHOLE, not cut into separate pieces. Sex must involve our whole self and this is why it cannot be done outside of marriage. Sex is “noble and worthy” as Pope Paul VI wrote in Humanae Vitae, and bears fruit, as anything else, when done according to God’s plan and will.

“Yet we must also understand that one of the absolutely holy, beautiful and sacred things that God has given to us is our sexuality.Sex is holy. Sex is sacred. We know that sex is holy because God uses it, joining his divine and creative power to the love of a man and a woman to bring forth new life into the world. No two people ever work so closely, hand in hand with God himself, as when they become co-creators with God and bring forth new life into the world. Although many people are probably not thinking about this at the time when they engage ins sexual relations, God is very present in that life-giving act, whether a pregnancy results or not... Every act of sexual intercourse is intended by God to express love, commitment and openness to life... Sexual activity is a gift that we give to another person to whom we have committed our lives. All too frequently sexual activity is seen as the taking from another for one’s own pleasure.” A Pastoral Letter on Cohabitation before Marriage – Kansas Catholic Conference. (Emphasis added)