We don't know anything about Orc females because the professor never included them in the narrative.
It is my personal belief that he left out this disturbing graphical image precisely because it was crude and he did not see a need for it. Note that we have virtually no sexual references in any of Tolkien's writing. I think that he didn't see it as necessary and probably only would have cheapened his creation.
Today's world is very different than the world that JRRT lived in. We expect today's stories to leave nothing out. That was not the case in the middle of the last century.
"Just like Mary Shelly, Just like Frankenstein, Break your chains, And count your change, And try to walk the line"