Oomis, I was always in agreement with you about not telling parents things that could cause them pain. From the vantage point of many years later, I can see they were definitely spared some pain, but they were also, inadvertently, distanced from us. It put them in the position of sometimes not understanding what was going on with us. They may not have beeen able to figure out exactly what the situation was, but they’re smart enough to realize there was something we were keeping from them. So the question becomes whether you prefer to give up the close relationship that mutual trust fosters, or whether you want to spare parents some pain. In the case of my own children I have been told things that definitely hurt, but in the long run, I’m glad I knew.
As for telling parents about a pregnancy- it’s a personal thing. Everybody has to find their own comfort level and share the news when they’re ready. I would hope parents and friends would have the intelligence to be happy whenever they’re told. And as others already mentioned, it’s (hopefully) not a secret you can keep forever anyway.