Well-wishers and press are waiting outside the Lindo Wing in London for a glimpse of the child.
The Duchess of Cambridge’s previous births have been relatively quick, and she has not spent days in the hospital.
After the birth of Prince George and Princess Charlotte, Prince William and his wife introduced their children to the world on the steps of the Lindo Wing.
So, what time will the couple emerge from the hospital for their first photos with the baby?
Kate was in hospital for just a little over 24 hours for the birth of Prince George in July 2013.
Her second birth was even faster. Kate spent just 10 hours at the Lindo Wing for the birth of Princess Charlotte in May 2015.
Since she went in to hospital early this morning, according to the statement released by Kensington Palace, the family is likely to be seen this afternoon.
After giving birth, Kate and William will enjoy some time with their new child before preparing for the waiting cameras.
It is believed Kate had her hair blowdried after the birth of both Charlotte and George, so she may do the same today.
Announcing Kate entering labour today, Kensington Palace tweeted: “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 Duchess travelled by car from Kensington Palace to the Lindo Wing at St. Mary’s Hospital with The Duke of Cambridge.”
One thing that won’t be announced immediately is the name of the newest Cambridge child.
Many are speculating on the name, and there are some very royal suggestions, while others have made more outlandish predictions.
For a boy there has been a last minute flurry of bets on the name James.
For a little girl traditional names are also considered to be most likely.
The leading contender is Alice, which has the highest odds, followed by Mary.
As this is Kate’s third birth, she is well used to the process of labour and delivery.
What can she expect after the birth of her latest son or daughter?
Birth is physically demanding and can lead to a number of effects, from stitches to piles.