I'm currently in my 28th week and I'm still taking Flintstones Vitamins Complete. I tried all the others that were prenatal over the counter and the ones prescribed by the doctor and they ALL made me horribly sick. Therefore, my physician said I could take 2 flintstones vitamins a day. Infact, she just had her baby several months ago and that's what she took and it worked out well for her. Also another option would be to go to a Whole Foods Market or natural food store and purchase children's chewable vitamins and for sure you know their products will not contain artificial dyes, preservatives and artificial sweetners.
All in all, make sure you eat healthy.