I am pregnant, an alum that's a student again, and married... I still don't think it presents a positive image. There will be some people who will associate you with your sorority and won't know your circumstances. Just my opinion...
I know, though, that it has been more appropriate for me to hold off from wearing my letters. I have the rest of my life to wear them. Nine months of not wearing them hasn't been a huge sacrifice in order to keep ZTA in a "positive campus image".
So, James, to answer your question: No. I do not think it's cool to wear letters if you are still on campus and married. And, I have some experience in this area...
Even though the baby was conceived out of love, some people on campus or even off campus might see a pregnant woman in letters as simply being a slut. (Alphafrog, please don't think that this is the way we perceive your situation... I am just making a point to James' comment.)
In an age where we sorority women have trouble with being seen as anything more than the stereotypical twits, it would serve us all well to err on the side of caution.
And, you know I love ya, James, but I don't think this is an issue any male should be commenting on. A frat guy can "knock a girl up" and no one will be able to physically tell that they have a baby on the way. They can still wear their letters without worrying about their image.
So, I propose that all men stay out of this issue. lol.