Hi Ladies, I am a lurker hoping to join you soon :-)
Tegam - I think when people ask you in a casual situation how many kids you have, they mean "living kids", they are just trying to figure out what your family looks like. I always tell them one, because the uncomfortable silence that would follow any mention of the miscarriage would be more uncomfortable for me than for them. I have lost my father when I was a very small child, and then when people asked me "what does your dad do" and I would say "he is dead" it was always very akward. I imagine it would be similar if I said "I have one living child and two angel babies" so I'd rather not drag them into the akwardness plus I do not want people to look at me with this "you poor thing" look at their faces. Never liked it.
When a doctor asks, then I tell them of course.