With my first pregnancy I needed to go up to a DD (from a D) when I was about 10w. I ended up getting a couple of "touched by Berlei" bras as they were sensationally soft, but still had an underwire.
I also gota new sports bra as I was still playing netball til 19w.

At about 25w my breasts started leaking colustrum, so then I got fitted into maternity bras. They were still a DD, but I gone up from a 14 toa 16.
I still fit all my maternity bras from last time, the cups in some are a little big, but I just cope with it.

While its important not to put extra stress on your boosies bduring pregnancy, I actually got fitted for a new push up underwire bra about 3m ago as I was sick of maternity bras. I had been in them for nearly 2 years!!!!! The woman at Myers tried to tell me I shouldn't be getting underwire, but I know what a blocked duct feels like, I'm pretty familiar with my breasts now (breastfeeding for 15m does that!!!), and I only wear the underwire bra maybe twice a week??? Its not that comfy, but it looks great, and my boobies look lovely and high in it - a novelty these days!