OK so I'm super short- about 5 feet tall.
I obviously don't have any answers for you being that I'm only about 6 weeks, but I'm also 5 feet tall and wondering the same thing. What was wrong with the fit from Old Navy? Was the length wrong? I've always found that Old Navy short fits me pretty well but I'd feel dumb going in and trying them on in the store and I don't want to order anything until I start showing.
Ann Taylor has a maternity line, too, but it's only online. I was looking yesterday and they don't have much but maybe enough to get you what you need in pants?
So I was disappointed in the Old Navy pants for 2 reasons.
I managed to get a pair of petite jeans and black pants from Motherhood (the black pants fit especially well). Other than that I cuffed or hemmed my pants :P I actually got one pair of Motherhood khakis at Macy's that was short enough to begin with that I could wear it with big shoes - no alterations required.
The Motherhood jeans were actually a little short for my liking, but I am almost 5'2" so they may fit you better.
Brita- You're right they fit!