When exposed to high amounts of mercury, children and babies may have problems learning, paying attention, remembering things, walking and talking. A developing fetus (or unborn baby), babies, children and teenagers are more vulnerable to the harms of mercury than adults because their brains are still developing, and it takes smaller amounts of mercury to cause health problems. During pregnancy, mercury can pass from a mother to the fetus. In smaller amounts, it can also pass into breast milk. Older children are also vulnerable to mercury because their brains are still developing.