Imagine the following scenario: a king in a patrilineal dynasty dies without a male heir. Therefore the crown passes to either his eldest daughter or to his closest male relative, and this person is installed as the new queen or king. It is subsequently discovered that the queen dowager is pregnant by the late king with a male child. What happens to the new monarch, then? Do they have to abdicate in favour of the child once it is born, or does they continue to reign until their natural death, after which the throne would pass to the queen dowager’s son?
I suppose answers will vary according to the rules of succession of a particular house, so feel free to answer for any house whose rules you may be familiar with.