But it's easiest when your baby is born without drugs in her system, and when she has unbroken contact with you until after her first nursing. Most alert babies nurse within the first hour, and that first nursing may be a very long one. Take your time and enjoy each other. There's plenty of time for weighing and measuring afterwards. Your Wardrobe already exists.
Most mothers just wear their regular two-piece outfits and pull the top up on one side to nurse.
The baby's body covers everything that the top doesn't cover. A bra is optional at all times of your life, and doesn't prevent sagging. If you want to wear one, make it comfortably loose so that it gives you easy access for nursing. Some stretchy ones simply pull up. Others have a nursing flap.