@ladyjane - It sounds like you may have shin splints. You should do proper leg stretches and plenty of warm-ups before you run to help prevent splints. An ice pack can help reduce the pain when it occurs, and sometimes alternating between hot and cold packs helps too.
Since you haven't been running regularly for awhile it might be wise that you try not to overdue it in the beginning. You need to build up your momentum as it may be impossible to start out say two miles or three miles where you were before you got pregnant.
Take a few days off to allow the shin pain to heal itself and then resume again with shorter runs. If you overdue it you could cause severe damage to your muscles and we don't want that to happen.