with #1 (dd) we told everyone very early on. dh had just gotten hom efrom iraq and we were shocked to say the least, though very happy about it. it never occured to us not to tell people.
with #2, we waited till 7wks and told the family at christmas. we had told dd right away too, though she was only 12mo. we even brought her to the u/s at 11+ wks and really talked up how she would get to see the baby and everything. thank God that she was too little to really understand any of it, because we found out at the u/s that the baby had died around 8wks or so.
#3 we didn't tell dd, but we did tell our families within a week of finding out. our thought was that it was very unlikely for lightning to strike twice right. we had another missed miscarriage, and i really wished we hadn't said anythng because the kind of "support" we got was not what we needed!
#4 we waited till we saw a heartbeat at 6+ and 8 wks. we thought we were out of the woods for the most part, so told our families again, and then went thru another missed miscarriage.
#5 (ds) we'd completely lost any hope of getting a take home baby so we told no one. we had weekly u/s from 7wks thru the end of the 1st trimester due to being so stressed about miscarrying again. not to mention, the only way we learned of (or even suspected) the miscarriages was thru u/s wks after the babies had died. my body never gave us any signs. after the 12 wk u/s, we told dd, who was just shy of 3 at that point. miraculously, she did great and did not tell anyone. we ended up telling family around 17wks and work at 20wks, mainly because it was impossible to hide at that point. it was nice to be able to just have the stressful part of the pg be just dh and i. i tend to be a very private person, and i wouldn't have wanted people asking how things were, etc. not to mention, i couldn't handle any more comments about how we needed to stop trying, were obsessed, etc if we went thru another loss.
#6 (to be determined

) we again waited till 12 wks to tell dd, adn 16 or so to tell family. we weren't nearly as nervous about things going wrong this time, but it was nice to not have other people worrying too and having that rub off on us. not to mention, ds will only be 17mo when this baby is born, so we didn't want to hear the comments about our family size, timing, etc.