I've had sex with two providers in the past who were pregnant. And I agree with the above posters that something happens with those hormones and they can become insatiable.
I saw a working girl years ago in a motel in East Dallas. This white chick was probably 7+ months along. I cruised by the motel and saw her standing on the walkway in front of the motel. Pulled in and asked her if she was available for a date. She said, yeah come on in. I hop out, go in to room, and sit on bed. She has large breasts and is 5' 7-8", I pull out my wallet.... bamm, it hits me...I'm broke. (lol). I only have a $10 bill on me. I look up at this very sexy girl and tell her the sad news. Guess what she does? She says that's okay I just really want to have sex right now! OMG
We then spend the next hour fucking like crazy. K9 was the predominant position, as I couldn't and didn't want to lay on her tummy. She was insatiable. I had msog, deep bbbj, and dfk... and left a complete sweaty mess! But, hell it was so worth it. Never had another crazy day like that since... but oh the memories!
So yes I'm a believer in pregnant women being horny!