Des Moines International Airport has a dedicated nursing pod for breastfeeding (optional) and breast pumping moms who need the space to use manual or electric breast pumps. The Nursing and Pumping Pod is located just past security in the terminal.
Des Moines International also has a family restroom that moms can temporarily use but lacking nursing mothers amenities. They also allow moms to use their business center room as a temp quiet and private space to express breastmilk for their babies. Of course you will need to make sure that room is not occupied.