The only bad(ish) reaction we've had about my pregnancy was from my OH's Dad. We announced our news at Sunday dinner (we were going to anyway, but we had to as his Mum kept offering me wine, and I don't usually say no!) and while she was delighted, jumped up and hugged me and OH, OH's Dad just looked utterly stunned. He didn't say anything whatsoever for about two minutes, and it kind of became a bit awkward as he was just sat there staring with a stunned expression while OH's Mum was happily chattering about how exciting it was, and OH's brother (who already knew) was pleased as well. Eventually he left the room saying nothing, and then came back and opened champagne, but it seemed almost as though he felt that was the correct thing to do rather than was genuinely happy. He has since assured us that he is happy, and seems more comfortable with it now, but it was incredibly awkward at the time!
We've only been together two years and aren't married (or engaged) yet, so I'm not sure if it was that, but we've known each other since we were seven, been really good friends since we were sixteen (I was his first kiss!), and bought a house together last year (and we were quite clear about wanting one with three bedrooms...) and he's 29 and I'm 29 next month so we're not exactly teenage parents or anything. So I was a bit surprised by his reaction! But he seems to have genuinely come round to the idea now, which is good!
The rest of our family, friends and colleagues have all been delighted to hear the news 