Is prenatal vitamins safe for teens (i'm 14) and up if you are not pregnant, and if so, which ones are best?

Need to grow my hair about 5 inches in the next 2 and a half months. (i know i'm going to get answers saying that's humanly impossible, but I'm not losing hope) Well, I have heard gr8 things about prenatal vitamins and I was wondering does anyone know any good brands that give solid results?