( CNN ) -- The news the Duchess of Cambridge is expecting a child marks a dramatic departure from previous royal pregnancies . For it is believed even the queen may not have been given the happy news . Buckingham Palace were forced to make the announcement only after Catherine was taken to hospital suffering from acute morning sickness . Usually proclamations of royal births are posted on the gates at Buckingham Palace only after the 12th week of pregnancy . But knowing it would be impossible to keep Catherine 's visit to hospital a secret , Buckingham Palace took the unusual step of pre-empting press speculation and revealing the news immediately . The announcement is in stark contrast to Princess Diana 's first pregnancy , which was announced some six weeks after the queen had been informed , and after months of intense press speculation . Royal advisors are being surprisingly open about Catherine 's condition , despite recent intrusions into her private life , including the publication of topless photos , which were condemned by Buckingham Palace . It is believed a new spirit of openness has been embraced by William and Catherine in an attempt to prevent the massive press interest and speculation that surrounded Princess Diana . Prince William drove his wife to hospital earlier today and spent hours by her bedside . He left tonight looking tense but happy . Catherine is expected to stay in hospital for several days . Catherine and William baby news sparks media frenzy . Sources said the couple are `` incredibly happy but nervous . '' In a statement on their website William and Catherine said they were `` delighted with the news . '' It is unclear when senior members of the royal family , including the queen , were told about the pregnancy -- but a palace insider says Catherine 's parents were already aware their eldest daughter was expecting because she was taken ill whilst staying at their family home in Berkshire this weekend . Catherine 's pregnancy could turn out to be one of the most significant in the history of the British royal family , for the child will accede to the throne even if she is a girl . The child will not be subject to the centuries old law of primogeniture , which puts male heirs ahead of women . Britain 's Prime Minister David Cameron has agreed a deal to change the rules on the royal line of succession , which means male heirs will no longer be given priority . News of the pregnancy was met with joy throughout the UK . Within minutes of the announcement being published on the royal couple 's website it had crashed under the weight of traffic . Photos : The Duchess of Cambridge 's best looks .
Palace forced to announce Duchess of Cambridge 's pregnancy after hospital trip . Unclear when senior members of royal family , including the queen , were told . Comment: Pregnancy could be one of most significant in the UK royal history .