Prince William and his wife Kate are "very pleased" to announce that they are expecting their second child, Kensington Palace said on Monday.
The prince's grandmother Queen Elizabeth II was said to be "delighted" at the news, which comes less than 14 months after the birth of the couple's first child, Prince George.
The couple's office, Clarence House, said the couple and their families were "delighted" with the news.
Clarence House said the duchess was being treated at Kensington Palace for severe morning sickness.
She suffered from morning sickness during her first pregnancy with Prince George, who was born in July 2013.
