Sterilizing removes bacteria and viruses better than any soap can. But, you don’t really need to sterilize your bottles after every single cleaning. It is a good idea to do it at least once a week or more, depending on how often you use your bottles though. You certainly can sterilize after every use if you prefer. It may give you peace of mind to know that your baby’s bottles and breast pump accessories are as clean as you can get them.