I have had this many times too, and I echo the posters saying the people who are negative like this are either A) Jealous and bitter. B) Unhappy and miserable and want you to feel as shit as they do. C) Wanting to present themselves as cool and more clever than you.
I say the last one (C) because IME people who are negative Nancies seem to be under the impression that they are smarter than you/better than you, and more cool and laid-back.
When I was getting married (in the 1990s) I told the 6 women I work with; only 2 of them said woo hoo congratulations.' The other 4 (all women) said 'what the fuck for?' with a kind of
look. I said 'umm because I love him.'
They were so negative, and derogatory and rude, and basically mocked me and took the piss. Unsurprisingly all 4 were single or divorced. I don't mean to be bitchy about single/divorced people, and I know many are happy with their single or divorced status, but these 4 woman were horrible to me, so I can only surmise that they were unhappy, and jealous of me.
Then when I said I was expecting a baby, I got nasty comments ranging from 'your life is over now,' 'why the fuck did you do something so stupid?' and 'LOL I can't wait to see YOU with a baby.' I even got one woman saying 'I thought you were pregnant, as I noticed you're getting fat.
I was 6 weeks gone, and my weight was the same as it had been for 10 years or more! 
I also got one colleague saying 'I knew you'd be pregnant next! Couldn't stand the attention Mandy got eh?'
'Mandy' had a baby 3 years earlier, and left the year before! Even several members of my extended family slagged me off and said 'YOU with a baby haha' and 'WTF are you thinking? Babies are hard work ya know! You can't palm them off on your mother when you feel like it.' (I wasn't planning on doing that anyway, and I never DID do it!!!)
Also, I had a couple of people put me down when I said we were moving to a little village ('WTF for? Village folk are horrible. Judgy and cliquey!' And 'LOL, YOU in a little village ha ha!') FYI, the people here are lovely, and we love it here.
But yeah, although most people have been perfectly nice over the years, a few of them have been rude, derogatory, and spiteful. And yep, I believe (in most cases,) it's jealousy, and anger that we have what they don't have, and can't get.''