Prince William and his wife Kate are expecting their third baby in April, Kensington Palace announced on Tuesday.
The couple -- the Duke and Duchess of Cambridge -- were "delighted" to confirm the month their child is due to be born, a brief statement said.
Kensington Palace announced Kate's pregnancy last month, after she was forced to cancel an engagement because of extreme morning sickness.
The duchess has continued to suffer from the condition, but made a surprise appearance at a royal engagement on Monday.
She is due to visit Norway and Sweden with William on an official visit early in 2018.
The couple already have two children: Prince George, born in 2013, and Princess Charlotte, aged two.
Both were born at St Mary's Hospital in London, where William was delivered in 1982.