Yes, babies do need waterproof mattresses. Waterproof mattresses are essential to a baby's health and comfort by protecting against wetness, dust mites, allergens, and bacteria. In addition to helping keep babies dry throughout the night, waterproof crib mattresses provide an important barrier against liquids that can seep into the mattress core. This type of mattress also helps protect them from asthma triggers such as mold or mildew, which can form in non-waterproof mattresses if they get damp or wet.