(ABC News) -- Prince William's wife, Kate Middleton, has given birth to a baby boy.
Middleton was admitted to the hospital to give birth, according to a Kensington Palace spokesman.
"Her Royal Highness The Duchess of Cambridge has been admitted this morning to St. Mary's Hospital, Paddington, London 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," the palace said in a statement today.
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Middleton was admitted shortly before 6 a.m. today with The Duke by her side, and she is progressing normally, the palace said. There is no suggestion that she was induced.
Prince William and Kate Middleton's firstborn will be third in line to the British throne, after grandfather Prince Charles and father Prince William.
The British Parliament is changing a 300-year-old law so that the baby will be the heir to the throne, whether it's a boy or girl. Under plans to change the rules of succession, if the baby is a girl, she will make history as the first girl to keep her place in line even if she later has a brother.
The reigning monarch, Queen Elizabeth II, was only eligible to rule because her father had no male children.
Elizabeth has been on the throne 61 years. This baby will be the queen's third great-grandchild.
Kate gave birth in the Lindo Wing of St. Mary's Hospital in Paddington, where Diana had William and Harry.
Prince William was the first royal heir to be born in a hospital instead of in the palace. The first sighting of him and Prince Harry was when their parents exited the hospital with the new princes in tow. William and Kate are expected to do the same with their new arrival.
It's unknown when the baby's name will be revealed. Harry's name was announced the day he left the hospital, but several days passed before William's name was made public.