Lee Rourke doesn't approve:
Sex does not belong on the page, not the type of sex scene we read in contemporary literary fiction anyway; for me, when I encounter it there, in countless modern lifestyle novels, it is a form of nothingness, hanging on the page, dislocated from the rest of the book.
When novelists try to make their sex scenes literary, when they try to orchestrate each moan and groan into the book, wasting all that time trying to create the perfect scene, trying to make it seem believable, they fail miserably. The literary approach to writing a decent, believable sex scene is the most embarrassing thing about contemporary literary fiction today.
Just do it.