Save for some basics (e.g. Jeans, black skirt), forget about special pregnancy clothes! They are generally made out of cheap fabric, make you look more pregnant than you are and - because of the complete absence of any consideration for current fashion trends - also older than you are. Simply look for cuts which accommodate your bump.
Good are empire line dresses (fitted at the bust and otherwise loose) and kaftan style tops. Great designers for this are DvF and miu miu. On the high street, Reiss is a good option. As long as your additional weight is limited to a bigger bust and the bump, there is generally no need to go up a dress size. A good investment are a couple of blazers - maybe a smarter and a more casual one - if you wish to disguise your bump a bit.