Congratulations Jelly! Hello Surrey 
Maternity bras are usually awful, non-wired bras with extra hooks at the back so that you can still wear them when your rib cage gets expanded by your baby towards the end of pregnancy.
Nursing bras are the same, but they've got hooks on the shoulder strap that you undo to expose a book for breastfeeding.
You can sometimes get soft wired versions and you can also buy back extenders for your normal bras. Converter kits to turn your normal bras into nursing bras are apparently available on amazon.
personally, I'll be in sports bras until the birth, then Emma Janes afterwards. They aren't pretty or shapely but I found them comfortable enough last time.