Prince William, Princess Kate reveal 3rd child due in April 2018

William and Kate are already parents to George and Charlotte.

"The Duke and Duchess of Cambridge are delighted to confirm they are expecting a baby in April 2018," Kensington Palace said in a statement today.

William and Kate, both 35, have not yet announced where Kate will give birth, but it is expected she will use the same hospital as with her previous deliveries. Both George and Charlotte were born at the Lindo Wing at St. Mary’s Hospital in London.

Kate has gradually added royal engagements back to her schedule as she feels up to it.

On Monday, Kate made a surprise appearance alongside William and Prince Harry at a children's charity event. Kate, sporting a new hair style, danced with Paddington Bear on the platform of Paddington Station in London.

"Her condition is improved, but the duchess does continue to be affected by hyperemesis gravidarum," a royal aide told ABC News Monday. "She is making decisions day to day but is keen to do as much as she can."

Kate also attended a Buckingham Palace reception on Oct. 10 to mark World Mental Health Day.

William and Kate were scheduled to go on a royal tour of Scandinavia later this fall. Kensington Palace announced today that instead William will visit Finland alone in November, a trip he will make at the request of the U.K.'s Foreign and Commonwealth Office.

Kate will join William on an official visit to Norway and Sweden in early 2018, according to Kensington Palace.

Earlier this year, William and Kate visited Poland and Germany with their children as part of a "Brexit" charm offensive as the U.K. negotiates its withdrawal from the European Union.