Buckingham Palace announces

The Duchess of Cambridge is pregnant!   Yes, the Duke and Duchess of Cambridge are expecting their first child.   The Duchess is in the early stages of pregnancy, and is suffering "acute morning sickness." 

This will be the couple's first child.    The child will be the third in line to the throne.  This will be the first time since 1894 since the Sovereign had three heirs in direct line to the throne:

Queen Victoria - the Prince of Wales - Duke of York - Prince Edward of York.

Queen Elizabeth II - the Prince of Wales - Duke of Cambridge -- baby Cambridge.

Will this announcement speed up the Commonwealth Parliaments and the British Parliament to promulgate new succession laws that allow for the succession of the first born regardless of sex. 

If the laws are not changed by the arrival of baby Cambridge,  a son will be HRH and a Prince, but a daughter will be Lady Christian name Mountbatten Windsor.  This is based on George V's Letters Patent in 1917 which changed the name of the house to Windsor, and limited the HRH to the children and grandchildren of the Sovereign in the Male line and to the eldest son of the eldest son of the Prince of Wales.

The children of the Duke and Duchess of York were not royal highnesses until 1898.  They were Highnesses (as great-grandchildren)

"Victoria by the Grace of God of the United Kingdom of Great Britain and Ireland Queen Defender of the Faith To all to whom these presents shall come, Greeting: Whereas by virtue of Our Letters Patent dates the thirtieth of January one thousand eight hundred and sixty four wherein We declared Our Royal will and pleasure in that behalf the children of the sons of any Sovereign of Great Britain and Ireland are entitled to the style of "Royal Highness" Know Ye that in the exercise of our Royal and undoubted prerogative and of Our especial grace We do hereby declare our further Royal will and pleasure that the children of the eldest son of any Prince of Wales shall have and at all times hold and enjoy the style title or attribute of "Royal Highness" in addition to such titular dignity of Prince or Princess prefixed to their Christian names or other titles of honour if any as they may otherwise possess Our will and pleasure further is that Our Earl Marshal of England or his deputy for the time being do cause these our Letters Patent or the enrolment thereof to be recorded in Our College of Arms to the end that Our officers of Arms and all others may take due notice thereof. In Witness whereof we have caused these Our Letters to be made Patent.. Witness Ourself etc."

The official announcement:

Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting a baby.
The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall and Prince Harry and members of both families are delighted with the news.
The Duchess was admitted this afternoon to King Edward VII Hospital in Central London with Hyperemesis Gravidarum. As the pregnancy is in its very early stages, Her Royal Highness is expected to stay in hospital for several days and will require a period of rest thereafter.
Notes to Editors
Hyperemesis Gravidarum is very acute morning sickness, which requires supplementary hydration and nutrients.