#1 "You're totally carrying up high/down low like a boy/girl baby."
Same thing for you look good so you must be having a boy/girl. Unless someone has told you what their ultrasound said (assuming they even want to find out) this old wives tale BS is not science. So you're only playing with the mind of the mother-to-be. Even ultrasounds aren't 100% accurate. Just shut up about it people, you don't know XY from YY from just looking at me.
#2 "You don't look pregnant from behind!" This is a back-handed compliment. When I first heard it I was excited, but then I realized - no one carries a baby in their ass, every woman carries up front. Which means if you look anything from behind, it's fat honey. And I just don't think women should make each other insecure about their fat behinds.
#3 "Should you be eating that?" I'm not an idiot. I know that a cheeseburger isn't good for my baby. I get the evil eye for drinking a Diet Coke. People, 9 months is a long time (it's actually more like 10 months, but they lie to you) to cut yourself off from calorie packed goodness/caffeine. Moderation is key. If you see me with a Diet Coke in my hand, you prolly just caught me at a weak moment. One cannot live on H2O and veggies alone. So lay off!