I learned the hard way early on not to tell anyone. I made the mistake of telling my mother very early that I was considering UC, and she totally lost her gourd. I tried to tell her that I'm not 100% sure it'll go that way (if I feel there's a problem, of COURSE I'll transfer), but that I was leaning heavily in that direction. For a while I got put through all the panic crap from her, at least until I started seeing a medwife in the hospital and laying down backup plans, which she now has in her head are primary plans (I'm going with the "oops" excuse). The few friends I have told have been supportive, but even the crunchiest of mamas that I've talked to consider it 'unwise.'
The point being, people are too steeped in our terrorculture to be supportive of something that they've always been told is inherently dangerous (oh please, if it were that dangerous, how could humans possibly be the dominant species?). Even if they're decent enough to keep their mouths shut about it and not try to terrorize you out of your decision, it's still hard for them to hear about, and that's far more difficult to cover up.
Honestly, I wish I hadn't said anything to anyone and just BS'd my way through the whole pregnancy. -_- I know deep down that this is what's best for myself and my child, and that inner voice is what I trust above any and all else.