Nursing moms traveling through Phoenix Sky Harbor Airport can also use the Family Restroom at D Gates Terminal 4 if the dedicated nursing mothers room in the Children's Play Area is too far away or occupied.
A mom submitted this area stating: "Family restroom just past Security near main restrooms in D gates"
Obviously not the ideal location for nursing because of a flushing toilet and others maybe in and out, but a backup for a quick nursing mom emergency.
Also don't forget, Arizona is a breastfeeding friendly state and moms can openly breastfeed anywhere in public if they are comfortable doing so.