Announcing the news Clarence House said Kate is suffering from the severe sickness she had with Prince George. She is being treated by doctors at Kensington Palace.
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William and Kate were scheduled to open the £21-million Dickson Poon building together
The royals were due to take part in a traditional Chinese ribbon ceremony at the Dickson Poon building, which is part of St Hugh's College. This involves the ribbon being cut in several places, meaning that more than one person can take part.
William will be welcomed by Dame Elish Angiolini, Principal of St Hugh's College, Baron Patten of Barnes, who is Chancellor of the University and was the last Governor of Hong Kong.
He will also meet Mr Dickson Poon himself, a Hong Kong philanthropist who donated £10 million of the £21 milion it cost to build the new wing.
The original Chinese studies centre was launched in 2008 but the new complex will provide 63 en-suite student bedrooms, a 100-seat lecture theatre, dining area and a range of conference and seminar facilities.
It will also contain a dedicated library and reading room, providing a permanent home for books from the Bodleian Library's China Collection.