Hi Kelly,
Ive so far decorated 4 rooms in my house since being pregnant, its fine dont worry, I checked with my midewife and she said not to worry. Just be sure your not stripping old lead based paints as these ARE harmfull.
I recomend decorating sooner rather than later. Im currently decorating the cloakroom toilet and I cant believe how tiring it is! and its a tiny room! I was going to do it in a day, now Im planning on spreading it out through the week. But like I say I have been painting, tiling, laying carpet, laying a patio, building a wardrobe, you name it during my pregnancy! just take it easy and dont over do it. any lifting, get someone else to do it and dont you be up and down step ladders either!