--are notable for increased amounts of iron and folic acid, designed for the developing fetus' needs.

The dosages in these areas are not huge, though--typically, 400mcg of folic acid--twice the amount used in most standard multivitamins (and twice the USDA mimimum daily requirement), and up to 27mg of iron, which is one and a half times the listed USDA minimum requirement. Thre may also be increased amounts of other B-vitamins--but usually not in the range many of us are used to taking in our individual supplements.

A prenatal vitamin probably wouldn't hurt you, but given the demands dysfunctional bodies make, it may not have enough of certain things to really help. In particular, there's usually not much more than the USDA daily minimum for D, calcium, magnesium, etc.

So--depending on what else one is already taking, it may not be adding in that much more.