Nappy covers, also called nappy wraps, are the waterproof outer part of a ‘two part nappy system’ where you will also need a separate inner absorbent layer (see inserts, fitted nappies, terries, and prefolds below). Waterproof outer nappy covers do not need to be washed after each use. You can essentially wipe them clean and just put a new, clean absorbent layer inside. As a rule of thumb, you can reuse the waterproof cover about 3 times, only once for a night nappy, and only once if your baby has dirtied in the nappy.