When I look at pregnant women I feel a mixture of envy (we're TTC) and also sympathy, as I feel that they have the most wonderful time - but also the hardest time - ahead. It makes me feel like I want to hug them and tell them to hang in there, and that it all gets easier so fast.
ETA: Just re-read that and realised how negative it sounded! Sorry, Jenrose - wasn't meant to sound that way. I just meant that it's really mixed emotions for me. DD is now 18mths and life has got better and easier every day. I found the 'newborn' days so hard, but now (with hindsight) they pass quickly and things just get more and more awesome. So, what I'm trying to say is that I don't think it's a cluckiness I feel - more a sense of "Wow - your life is about to change so much, and it will be hard but it will be the best thing you have ever done."
Don't think I'm putting it very well. I totally get how people would get clucky over pregnant bellies. As a PP said - it's a reminder that there is a baby in there!