Bosola's musing over what's happened, now totally sure that the Duchess is giving birth.
He occupies himself by being rude to the old lady again (seriously, Bosola needs a time-out for the way he treats this woman) for a little while until Antonio comes in, ordering some other courtiers.
Antonio gathers all of the officers together and tells them that he wants the court gates shut up and all of the officers locked in their chambers.
Antonio tells the officers that the Duchess is really sick in her room, but that somebody has stolen a lot of her jewelry and money so she wants to have the officers locked up and to be given the keys to their personal chests.
Afterwards, Antonio secretly tells Delio that the Duchess is giving birth, and that he needs Delio to ride to Rome ASAP. Why? Not clear. Perhaps to check on the evil brothers?
Cariola comes in: "congrats, Antonio, it's a boy!"
In his first thirty seconds of fatherhood, Antonio does the natural thing: goes to get a horoscope for his newborn son.