How does he know God intended for the rape to lead to pregnancy? God gave us the free will to sin and He gave us nature. Sins, such as rape, impact our physical nature and our spiritual nature, but I wouldn’t say that it is God at work. I would say instead it is people working against God.
“Before I formed you in the womb I knew you, and before you were born I consecrated you; I appointed you a prophet to the nations.”
-—Jeremiah 1:5
He has a destiny for all of us. How we enter this world shapes and molds us and prepares us for the tasks at hand.