Prince William says there is "not much sleep" happening at home at the moment.
The 35-year-old royal and his wife Duchess Catherine announced they are expecting their third child together on Monday (04.09.17), and during his first public engagement since the news was announced, William said they were "anxious" but thrilled to be becoming parents again.
Catherine is once again suffering from Hyperemesis Gravidarum - a debilitating form of serious morning sickness - but he has assured she is on the mend and once she is back on her feet they will be celebrating.
Making a speech at the National Mental Health and Policing conference in Oxford on Tuesday (05.09.17), William - who already has Prince George, four, and two-year-old Princess Charlotte with his 35-year-old spouse - 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. There's not much sleep going on at the moment."
The British royal couple surprised the world with their announcement earlier this week.
Kensington Palace said in a statement: "Their Royal Highnesses the Duke and Duchess of Cambridge are very pleased to announce that the Duchess of Cambridge is expecting their third child.
"The Queen and both their families are delighted with the news."
Catherine was forced to cancel a planned official engagement in London later in the day because of her morning sickness, which she also experienced when she was carrying both George and Charlotte.
The statement concluded: "As with her previous two pregnancies, the Duchess is suffering from Hyperemisis Gravidarum. Her Royal Highness will no longer carry out her planned engagement at the Hornsey Road Children's Centre in London today. The Duchess is being cared for at Kensington Palace."
William's younger brother Prince Harry was one of the first to congratulate the couple on their baby news.
The 32-year-old royal told reporters: "[It's] fantastic, great. Very, very happy for them."
And he also told well-wishers that Catherine is doing "OK" despite being poorly.
He said: "I haven't seen her for a while but I think I she's OK."
The arrival of the royal baby will see Harry bumped to sixth in line to the throne, behind his father Prince Charles, brother William and his sibling's brood.