If you look at alot of the fashion magazines its almost as if pregnancy is not era in the women's life.
This period that usually covers 9 months plus the breastfeeding of approximately 6 months overtakes our fashion decisions for well over a year. (Multiply that by the number of kids you're planning).
I have been looking around for a while now. Gap Maternity has some great options, as well as the Turkish brand Bellamom, but a great internet find is http://www.asos.com/.
Here's a round up of some of the styles that caught my eye...