I am an esthetician, and we usually don't do microderm on pregnant women because it's very harsh. When you're pregnant, you tend to have more sensitive skin because of the extra blood flow. Same goes with waxing.
My suggestion would get a glycolic peel of some sort... glycolics are safe during pregnancy because they stay on the surface of the skin... they don't go through the blood. However, you don't want to get a salicylic acid, because it does go through the blood. I have done lots of glycolics on guests and they love it because it actually exfoliates just as well. You can probably buy one or you can get it done at a spa. I LOVE doing glycolics because it makes my skin so soft. It chemically exfoliates by forcing skin cells to slough off. Leave it on for about 3-5 minutes and do it about once a week and eventually work up to twice a week.
You'll love it.