We won't be telling anyone not directly involved with the birth until after the baby is born. We still have to figure out child care, which could be a bit tricky since we just moved here and we don't have any friends yet. With #1, we called my mom and MIL which resulted in lots of "checking in" calls that annoyed me and my midwives. Ha! My mom is a huge worrier, so it's much easier on everyone if she just doesn't know about it until after the fact. With #2, we didn't call anyone until after the birth and it was so nice! Of course, I went into labor at 4am and she was born before 9am so it's not like we had much time to make phone calls anyway. Still, I loved that it was all on our terms, and nobody was pestering with those "where's the baby?!?!?!" questions.
Hopefully I'll be feeling super high and excited after this baby is born, and if that is the case then we'll be calling everyone to let them know. I tend to get very silly after my babies are born and I love to share the happy news as soon as I can. I know this time will be different since we have two older children instead of just one, so I know we'll have a lot more to take care of, but I imagine we'll be welcoming any available visitors/meal givers/gift bestowers soon after the birth.
I think it's important to guard that desire of privacy, especially during such a magnificent experience. If you feel the need to not tell people, then don't tell them and don't feel guilty about it!