Most people wouldn't have announced to many of their friends and family by then, let alone have it national news. Their hands be forced really, there's no way they could have kept something like under wraps these days. Kind of a shame for them and must be really miserable for them even without the media circus. But fuck it, they're the royal family, comes with the territory.
8 weeks isn't stupidly early anyway. 12 is the standard but by 8 weeks you're past the most common period for miscarriages.