I think it all depends on the situation.
If it’s the couples first pregnancy, or after a very long break- parents should be told pretty early on – they worry so much & daven… don’t you think they deserve to know?
Otherwise I don’t think it’s neccesary to share till later (but before it shows…)
But, there are all kinds of circumstances… Some woman need to lay at the begining… some are terribly nauscous & weak, while others feel perfectly fine. It would be silly to keep it a secret when you can get the proper help you need if you would only open your muoth…
Friends & siblings are in a different category & it all depends how close & how desperate you feel to share either for emotional or physical needs/help…
There is something to keeping things quiet- things that are hidden from the eye are blessed, & everyone wants the pregnancy to go well!
I do beleive though, that even if it’s not for a long time (a couple of days/weeks) – there should be some time that it’s only the couples secret!