Until mum's milk comes in and their supply settles to meet baby's demand, new mums won't know what size nursing bra they need to buy. (charlottekeating.com)
If you are able to, go to a store where you can be fit for the right size nursing bra. (bellefit.com)
To estimate what size nursing bra you'll need, you could take your measurement at 28 weeks and add 1 - 2 additional cup sizes. (mayarya.com)