Citric acid is safe, as far as I know. Of course... all things in moderation. :)
I think the only problem with citric acid is it might give you reflux or heartburn or indigestion. I have never heard of anything in regards to it harming baby! But definitely do some more research. I drank a ton of OJ during my pregnancies and it is packed with citric acid. The Vitamin C is VERY good for you and baby!