Human reproduction is so much more than just biology.  Physiology, psychology, theology, sociology. It is temptation and fear.  It is both complex and simple, idealistic and gritty.  There is a quote in a beautiful book by Thomas Howard that I'd like to share.  From Hallowed be this House, alternative title, Splendour in the Ordinary:

"...this act (physical intimacy) is an important picture of the mystery of divine love.  In that love, self -giving turns out to be the way toward joy and freedom and we have a vivid picture of this in the sexual act.  Here the whole thing is a jumble of giving and receiving..."

"It is a picture so hilariously vivid that we must either laugh aloud with delight at this divine comedy, or turn away in sheer incredulity--or embarrassment, perhaps, that the high mysteries should be thus served up to us."

"...with all our high notions of ourselves as intellectual and spiritual beings, and the most profound form of knowledge for is a plain business of skin on skin.  It is humiliating.  When two members of this godlike, cerebral species approach the heights of communion between themselves, what to the do?  Think? Speculate?  Meditate?  No, they take off their clothes."

In his sentence, "It is humiliating." we could observe a puritanical stance...this is naughty, it humiliates us...but I think it would miss the point.  In the act of union we are not humiliated...we are humbled.  By the simple biological facts of the purpose, needs and desires of our physical selves.  We allow ourselves to be vulnerable, and are then sanctified.

He banters about the idea in this book that the most ordinary or events in our life we spend time dignifying, and rightly so, we raise them up to be extraordinary, and the most profound events of our lives, birth, union, death...are quite undignified.  GRITTY.  Those sacred events, so overwhelmingly human and gritty and profound that we raise them up in language more than all the other life events.
Perhaps in this strange juxtaposition,  we are allowed a glimpse into the contradiction of Christ's  life, divine and human, profound and gritty.  Whose kind of God dies on a cross?  In the baseness of His death, all the beauty of heaven and earth is found.  In that humbling act, and allowance of vulnerability, we receive our most sacred gift.