I hid my last one because, having just dealt with a miscarriage that everybody knew about (and it was great to have support, but also saddening to lose the friends who couldn't deal with my grief) it was nice to just keep this one to myself. I didn't tell my family because I was emigrating to Scotland and wanted to surprise them with my big belly at the airport but they found out 2 weeks before when DH accidentally let it slip over the phone. That wasn't until 18 weeks though.