Jenn, as Heather said, saying you're sorry is an appropriate response even if you don't really know what else to do or say. One thing I thought of that you could ask is "Do you want to tell me about her?" That gives the mother a chance to say either "Yes, I would" or "No, I'd rather not". And you can take it from there. I really appreciated the people who asked me that question, because I did want to talk about Michelle but they couldn't have known that without asking me and I didn't want to make them uncomfortable either.
I was trying to find some resources on the web for family and friends of grieving parents, guidelines on how to act and how to help, etc. -- if I find some I'll pass them along. Thanks for caring...and I'm very sorry to hear about your loss, of course it must have been just as painful to you as our losses are to us.
Mommy to Michelle Elizabeth, 8/25-9/1/04, 24w1d, 1 lb 3 oz, severe PE/HELLP syndrome
Michelle's memorial page: http://www.geocities.com/jfiorello68