David's Bridal has some maternity options (or at least some options that can work for pregnant gals) in its lineups of bridesmaid dresses and matching outfit pieces that may work well for you--many of them are NOT the un-rewearable bridesmaid dresses of yesteryear.

Or select a gathered empire-waist style--they are very "in" right now, and depending on how advanced your "bump" is, you could perhaps go up a size to accomodate it.