The Duchess of Cambridge is well after an "anxious" start to her pregnancy, the Duke of Cambridge has revealed.
Making his first public appearance since it was announced he is to become a father for the third time, William said: "It's very good news."
He also said there was "not much sleep" being had at the main family home of Kensington Palace with Kate, who is less than 12 weeks pregnant, suffering from severe morning sickness.
The Duke thanked well-wishers during a visit to the National Mental Health and Policing Conference in Oxford on Tuesday, where he addressed officers as the event's keynote speaker.
He said: "We need Catherine to get over this first bit and then we can start celebrating.
"It's always a bit anxious to start with, but she's well."
He added: "There's not much sleep going on at the moment."
The new baby will become the fifth in line to the throne behind older siblings George and Charlotte, pushing Prince Harry into sixth place for the first time.
The announcement came as Prince George is expected to start his first term in school in Battersea, south-west London, on Thursday.
In his address to officers at the conference, William spoke of the importance of being open on issues of mental health.
He said he had been affected by the tragedy of Grenfell Tower and his encounters with people with poor mental health while working as an air ambulance pilot.
He said: "The tragedy of Grenfell, and the conclusion of my work as an air ambulance pilot, spurred me into doing what I can do to support you in a practical way."