In the last few wekks of my first pregnacy I was feeeling crappy, and my doctor told me it's totally safe to take the full dose if I wanted to.
As long as you don't go over the stated dose, or take them more regularly than the directions say, you are totally fine.
It's asprin you shouldn't take at all.
Hope this helps- he also told me that it was safe to be taking the full doese, as per the directions for more than a few days without harming the baby.