Here's a picture of me in one of my 10 gore dresses.  This one's parti-colored in burgundy and black corduroy with pewter buttons all down the front and up the sleeves to the elbows.  The sleeveless undershift (which I try not to show) I later modified with an extra panel down the front to conceal nursing slits along the sides.  I still have to unbutton the cote-hardie to access it, and since it has a train, I don't wear it with a surcote.  Therefore, I feel like I need privacy or a blanket over my shoulder to nurse in it. 

The reflection off the buttons gives away my pregnacy curves.  I couldn't wear it the next week.  My belly popped out!

See Motherwear.com's site for ideas on how to conceal nursing access.