I am 32 weeks pregnant, have various sizes older maternity and nursing bras. currently wearing a 36 band. cant remember if band size goes up or down after pregnancy so if I should be buying tight or loose nursing bras. I quite like the style and pricw of some h and m ones at the moment so would like to buy soon if I can
Unfortunately I've found you can't really predict what your boobs will do.
At the end of your pregnancy your rib cage spreads a bit and back size obviously goes up, this will go down again after birth. Your cup size will normally increase when your milk comes in, but may settle at a slightly smaller size if you bf long term.
For now i'd make sure you're in the right bra size - get measured at bravissimo or similar (not mothercare! Or m&s) measure yourself up for a rough guide to start with.
I am too tiny for bravissimo I would be laughed out of the shop!! I normally do have a bigger cup size when bfeeding which goes back down after a few months. but I need a bit more room to put breast pads in as I like the thicker washable ones.
There's a good explanation here if bra fitting without adding numbers give it a go! I used to wear 32a's! Now not bf I'm a 28dd/e which fits vastly better no boobs popping out the bottom, and a 28ff bf.