It should be fine, but ask your doc just to make sure. I was taking 400mcg of folic acid while pregnant, and had no problems. ( i wasn't taking a prenatal vitamin, was taking Flintstones )
Here is what I found
"Folic acid is a water-soluble vitamin, so your body will flush out the excess if you consume too much. For some women, however, getting too much folate may hide a B-12 deficiency, which is sometimes a problem for vegetarians. Ask your doctor or midwife if you think you may be at risk."
"During pregnancy, the recommended dose jumps to 600 to 800 mcg, or 0.6 to 0.8 mg. Of course, some women's needs are different. If you have a family history of neural-tube defects, you should probably get 4,000 mcg (4 mg) of folic acid a day. Talk to your doctor about how much you need before and after you conceive."
Good Luck and hope you have a happy and healthy pregnancy!!!