I have a huge impregnation fetish, to the point where I almost need at least the risk of pregnancy in a story or roleplay to make it hot, if not make it the outright goal.
So yes, I am turned on by pregnant women, but it's the same way I'd be turned on by the same woman if she weren't pregnant. If she's attractive to me, then she's attractive.
Now, the thought of fucking or raping a girl I impregnated is hot...especially if she's pregnant against her will, the result of my rape seed deep inside of her. I could mock her about how she "let" me come inside of her and fuck her with no condom. Didn't she know she'd get pregnant? And of course, I'd make her take all of my come inside of her each and every time, even though there would be no biological reason (she's already pregnant!). It's all about the pleasure for me, and the shame for her.