Wow, some people can be so rude, chunky, and I don't blame you for being offended!
I agree with passmethecrisps, I think by your thirties you are a lot more mature and more capable of raising a child, there are so many young mums out there who are battling with growing up and being a parent, and that isn't fair on the child.
Don't get me wrong, like I said before it depends on the person, i've always been mature for my age and have always wanted kids (I remember at about the age of six asking my mum if i'd be a good mum) and think having children at my age was the right choice for me. (I planned to have my first at 21) Although i've always considered myself a fairly young mum!
But I would never judge somebody for having a child in their thirties, what a ridiculous thing to be judgemental about!
Anyway, sod what other people think 
shinyblackgrape - I'm surprised they didn't make you do any jiggling or anything at your scan aswell, my baby was on it's side for a while and the sonographer sent me off to pee to give him/her more space to roll over, and had to wobble my tummy (v. embarrassing) to encourage the baby to wake up and move. I wouldn't worry though, as we all know babies are nocturnal creatures so the fact it was having a snooze isn't unusual!