Calcium and iron, when taken at the same time, bind together and your body can't absorb either one. This is why most multivitamins contain only a small amount; also, calcium is so bulky that trying to stuff enough calcium into a vitamin pill would make it way too big! The nurse who told you you were getting plenty from your prenatal certainly did NOT know what she was talking about, unless she quizzed you on your diet and determined that you were getting plenty of calcium that way.
There is an old saying that for every baby a woman has, she loses a tooth (something like that). This comes from the fact that your body will pull calcium from your stores (mostly bone) to ensure that the baby is getting what it needs.
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Calcium in prenatal or multivitamins
