i was a 36gg but am now a 38h, well was two weeks ago when i was measured and they seem much more massive now!
Maternity bras are totally the way to go IMO, soo much more comfy, much more support, more like a sports bra, with room to grow as well. Underwired bras are great for big boobs but only allow them to be one size and one shape, and mine seem to be growing all around, so out at the sides as well so underwired was sooo uncomfortable, actually gave me pain in my shoulders cos of the lack of proper support.
Mine are from M and S and were a 2 pack for £25, the lady fitted me to the biggest size that still gave me great support so i had room to grow, so i don't have to go back anytime soon. hopefully x x