So happy for them!!!
A May arrival would put her somewhere between 15 and 19 weeks. Though she could be 20ish and their just saying May in case she goes late. Whatever the reason for “delaying” the announcement is I will say that I like it when royals wait a bit to announce. Granted some are forced to announce sooner do to complications but there’s no rule that says you must announce at 12/13 weeks. I would think it’s nice to wait as long as possible to ensure everything is going well and to shorten the hoopla time around your pregnancy as much as possible. A lot of my friends wait until as “late” as 24 weeks (viability) to announce to the world...with family and a few people at work knowing sooner.
According to stories my mom had a relatively small belly during her pregnancies, she didn't show much. Besides that she was pregnant in the '70s and '80s, in which she was allowed to wear oversized clothing for most of the time
So she could keep her pregnancies hidden aka secret for a considerable long time. It was said my grandmother (maternal side) always correctly guessed my mothers pregnancies, something about seeing it in they eyes of the mother to be.