Dozens gather outside hospital to welcome the baby princess

The Duchess and Prince William and baby are expected to leave the hospital later today.

Britains Prince William, Duke of Cambridge (R), holds his son Prince George of Cambridge as they return to the Lindo Wing at St Mary's Hospital in central London, on 2 May, 2015 where his wife Catherine, Duchess of Cambridge, gave birth to their second child, a baby girl, earlier in the day. Picture: AFP.

JOHANNESBURG - Dozens of Britons are gathered outside the St Mary's hospital in London this afternoon hoping to catch a glimpse of the latest addition to the royal family.

Duchess of Cambridge Kate Middleton and husband Prince William welcomed their baby girl into the world this morning.

The royal family's newest member was born at 8:34 am, some two and half hours after Middleton was admitted in the early stages of labour to St Mary's Hospital, West London, the couple's Kensington Palace residence said in a statement.

The baby, whose name has yet to be announced, weighed 8 lbs 3 oz and William was present at the birth, the palace said.

"Her Royal Highness and her child are both doing well," it added.

The baby princess will be fourth in line to the throne behind her brother George, father William and grandfather Prince Charles, pushing her uncle Prince Harry down a place in the royal hierarchy.

As CNN's Max Foster reports, the family are expected to leave St. Mary's hospital later today.

"We have seen a visit from Prince George, that's one of the suggestions as to why they might come out today. If they've got a young child at home they'd want to get home faster than if they didn't have a baby at home so there's less likelihood of them staying overnight."

Members of both families, including the Middletons at the St Mary's hospital, are believed to be in London to welcome the princess.

Both families of the couple had been informed, including the new baby's great-grandparents Queen Elizabeth and Prince Philip. She becomes the 89-year-old queen's fifth great-grandchild.

The birth will provide a welcome distraction for many Britons from the country's knife-edge general election campaign, which comes to a head with the vote next Thursday.

Earlier today, analysts made speculations about the gender saying a baby girl could boost the British economy by a billion dollars.

There are also suggestions that the birth will influence the UK's upcoming general elections.

Royal historian Kate Williams said, "We all thought the baby would come in mid-April, that it wouldn't have any effect, but now she has come in close and people do say it would provide a boost to the government that is already in power, namely the Conservative government with David Cameron."

Prince William has reportedly taken paternity leave and is visiting in the maternity ward.

Kensington Palace says both mom and baby are doing well.

Prime Minister David Cameron tweeted: "Congratulations to the Duke and Duchess of Cambridge on the birth of their baby girl. I'm absolutely delighted for them, while Labour leader Ed Miliband said the news was fantastic and added "I know the whole country will be wishing them well."

The birth has also provided a boon to the country's bookmakers who having first offered odds on the child's likely gender, now turn their attention to names, with Charlotte, Alice, Victoria and Elizabeth the current favorites.

Slightly longer odds are available on Diana, Eleanor and Alexandra.

William, 32, was born at the same hospital to the late Princess Diana in 1982.

He and Kate, 33, met as students at St Andrews University in Scotland, married in a spectacular ceremony at Westminster Abbey in April 2011. Their first child, George, was born in July 2013.

When Kate leaves hospital, the couple will return to Kensington Palace in central London for a couple of days before heading to Anmer Hall, their country mansion on the queen's Sandringham estate in Norfolk, eastern England.