If she has had the baby then I do think it's a bit off if an announcement isn't made. All royal births in recent years have been announced on the day or within 24 hours, including the birth of Zara's recent baby.
Assuming mum and baby are both well then there is no need for secrecy. I understand their wish to have some private time but that doesn't preclude an announcement. Harry and Meghan can't just choose to be royal when it suits them.
I don't actually think she's had the baby yet though.