It's called pica. Pica is when you crave non-food items during pregnancy like ice, dirt, ashes, clay, chalk, laundry starch, baking soda, soap, toothpaste, paint chips, plaster, wax, hair, coffee grounds, and even cigarette butts. It may mean you have a n iron deficiency, but that's not necessarily true. Just don't eat ice to replace real food (obviously), and the worst it will probably do is hurt your teeth.
Lauren