Yes, as others have said you’re most likely to miscarry in those first 12 weeks and I think most women keep it quiet before then because it’s too hard to tell someone, if they get excited/happy for you and then you miscarry and have to tell them you’ve had a loss it can be very painful - especially alongside all your other feelings at that time. Extra hard if you’ve told a few people and have to tell them all.I’ve got to disagree about the 12 week thing, I think it’s to protect yourself as well in case something does happen and you’re then having to explain that trauma again. I think talking miscarriage is entirely down to you and how you feel and you have a choice to is disclose or not, when you’ve told everyone, that choice is taken away.
Plus - it’s quite nice to just be in that bubble before people start going on at you and offering unsolicited advice
Of course you can miscarry at any time but you’re generally less at risk beyond then. For me personally I think it’s easier to tell someone you’ve had a miscarriage and thereby revealing you were pregnant in that moment, rather than them knowing beforehand. You can still receive support and comfort, but it seems more in control somehow (speaking from experience ).
But as posters say, very much a personal thing and up to the individual on what works best for them. I do think people are more open about miscarriage and fertility than they used to be and it feels less taboo.