There is a band of stretchy fabric in the back that allow for stretch right around the bump (as if it was made for maternity as well). (lynzyandco.com)
Most definitely have the same problem with stretchy fabrics on my bottom half. (kendieveryday.com)
It's simple clip adjustable straps, drop down cup design and stretchy fabric makes a super comfy nursing bra. (blog.guguguru.com)