Pre-natal usually have higer dossages of calcium and iron, in addition to the folic acid and low vitamin A. Not only does calcium inhibit irion absorption, but the high levels of iron can cause constipation. I complained about the iron to my OB and he just said to take a children's chewable vitamin with a folic acid supliment. If you have a vitamin combination that you like and you're getting enough calcium and folic acid, aren't anemic, etc. by all means keep taking it.