Just don't answer them. Doesn't really matter if it draws attention to it, does it?
I can't explain it, but I sometimes don't like the intrusion and feel that frankly, beyond a 'he/she's born safely' the details are off limits. The details are boring anyway to anyone else. Why would you want to know.
There are only a few people I would tell about the birth of my second and to be honest no one would ask about her weight. With my first I did feel prompted to tell people as she was born at 8 months. But I can't recall it being a big deal. People never even asked whether it was natural or section.
I am a curmudgeon with very few mum friends and basically no family apart from my mother, so I will never have a clucking brood of relatives asking when it's due, have I had it, how was it, etc. I don't use facebook or twitter so wouldn't announce it there either.
Don't know why, but it annoyed me when my neighbour asked the sex of our baby of my husband. And then told him she was 'sorry, you wanted a boy, didn't you'. The berk.
Go incommunicado, like me!