Duchess of Cambridge Kate Middleton in labour

The Duchess of Cambridge, Kate Middleton, has gone into labour, Kensington Palace has confirmed, with royal-watchers now eagerly awaiting news of the third royal baby.

"Her Royal Highness The Duchess of Cambridge was admitted to St. Mary’s Hospital, Paddington, London earlier this morning in the early stages of labour," the Palace announced via Twitter.

"The Duchess travelled by car from Kensington Palace to the Lindo Wing at St. Mary’s Hospital with The Duke of Cambridge."

The Duchess, 36, is set to welcome her third child with Prince William as the world's media gather outside the hospital.

All three of the couple's children have been born at St Mary's Hospital - Prince George on July 22, 2013, and Princess Charlotte on May 2, 2015.

The hospital's exclusive Lindo Wing is also where Princess Diana chose to give birth two her two sons, Princes William and Harry.

A pregnant Duchess of Cambridge at an Easter service in Windsor on April 1. Source: Getty
A pregnant Duchess of Cambridge at an Easter service in Windsor on April 1. Source: Getty
The Duke and Duchess of Cambridge with their children George and Charlotte in 2016. Source: AAP
The Duke and Duchess of Cambridge with their children George and Charlotte in 2016. Source: AAP

The Duchess of Cambridge announced her third pregnancy last September.

The gender of the couple's third child is not known, but once she gives birth, the Palace will send out a tweet and Instagram letting the public know the time of birth, the baby's weight and gender.

The Duchess' pregnancies have been affected by hyperemesis gravidarum, in which women suffer from severe nausea and vomiting throughout their pregnancy.

Soon Prince George and Princess Charlotte will have a little brother or sister. Source: Getty
Soon Prince George and Princess Charlotte will have a little brother or sister. Source: Getty

Her last official engagement was in late March.

As the Duchess of Cambridge's due date drew near, royal watchers began camping out in front of St Mary's Hospital's Lindo wing - many dressed in Union Jack outfits.

Excitement builds as royal-watchers gather for the impending announcement. Source: AAP
Excitement builds as royal-watchers gather for the impending announcement. Source: AAP
The Duchess has gone into labour at the Lindo Wing of St Mary's Hospital in Paddington, London. Source: AAP
The Duchess has gone into labour at the Lindo Wing of St Mary's Hospital in Paddington, London. Source: AAP

The baby Prince or Princess will be fifth in line to the throne, and the Queen and the Duke of Edinburgh's sixth great-grandchild.

The Duchess of Cambridge's first child, Prince George, took 10 hours to deliver - but Princess Charlotte was delivered in just two and a half hours.

What will the royal baby’s title be?
The royal baby’s title will be HRH Prince or Princess of Cambridge and, if born today, will celebrate his or her birthday on St George’s Day.

The baby prince or princess will be born fifth in line to the throne, the Queen and the Duke of Edinburgh’s sixth great-grandchild and a younger brother or sister for Prince George, four, and Princess Charlotte, two.

A royal enthusiast waits outside St Mary's Hospital. Source: Getty
A royal enthusiast waits outside St Mary's Hospital. Source: Getty

Do the Duke and Duchess of Cambridge know their baby’s sex?
William and Kate chose not to find out whether they were having a girl or a boy at their scan. They opted to do the same with both of their two other children, Prince George and Princess Charlotte.

What will the royal baby be called?
It’s thought that the royal baby might be called Alice, if a girl, and Philip, if a boy. Other favourite monikers include Alice, Alexandra, Elizabeth, Victoria, Arthur, Albert, Frederick and James.

Princess Charlotte was born at the same hospital as her older brother in 2015. Source: AAP
Princess Charlotte was born at the same hospital as her older brother in 2015. Source: AAP

How long will the Duchess of Cambridge’s labour last?
When Prince George was born in July 2013, the Duchess gave birth 10-and-a-half hours after being admitted to hospital.

However, Princess Charlotte was born in May 2015 just two hours and 34 minutes after Kate arrived at the Lindo Wing.

The Duchess’ third labour could be even faster than her previous two. While it varies from woman to woman, some mums report quicker labours with each baby.

It's thought that the Duchess of Cambridge's third labour could be faster than her previous two. Source: AAP
It's thought that the Duchess of Cambridge's third labour could be faster than her previous two. Source: AAP

Clare Livingstone, professional policy adviser at the Royal College of Midwives, said: “It will vary from one woman to another. Some women report a quicker labour with their third baby but not everyone.

“It seems to be though that they do go more quickly. It’s a very individual thing.”

When did the Duchess of Cambridge go on maternity leave?
The Duchess went on maternity leave on March 22, but was seen at church with the royals on Easter Sunday in Windsor on April 1.

Who else was born on April 23?
If born today, the royal baby will share his or her big day with the likes of William Shakespeare, J.M.W Turner, Shirley Temple, wrestler John Cena, actor Dev Patel and model Gigi Hadid.

The royal baby news comes after the Royal Family celebrated the Queen’s 92nd birthday at the weekend, with a concert at the Royal Albert Hall.

The Duchess of Cambridge's sister Pippa and her husband James Matthews are expecting their first child. Source: Getty
The Duchess of Cambridge's sister Pippa and her husband James Matthews are expecting their first child. Source: Getty

Also this weekend, the Duchess of Cambridge’s sister, Pippa Middleton, was revealed to be expecting her first child. Pippa married her husband James Matthews in May 2017.