Bras should securely support but not bind under the breast. Constricting the breast could affect milk flow.
Breasts continually change in both shape and size throughout pregnancy. Choose a bra with a roomy cup design so that the breasts can expand once your milk comes in.
The upper side of the cups should be loose without sacrificing comfort or support. If breasts enlarge beyond a couple of sizes, refitting may be necessary.
Try on bras with a breast pad or shield. Place the pad inside the cups to check for fit.
The center of the bra should lie flat against the breastbone and the bra shouldn't ride up in the back. Ride-up indicates that the band may be too large, the cups or shoulder straps too tight, or the need for more support.
The bra should fit comfortably when fastened on the middle row of back hooks. This will allow for changes in body size as the pregnancy progresses and after delivery.