British royal officials say Prince William's wife, Kate, has been admitted to the hospital and is in the early stages of labor.
Officials said Kate and William, who spent the weekend at Kensington Palace, traveled to Saint Mary's Hospital in central London just before 6 a.m. ((0500 UTC)) on Monday.
Under a new law, still to be enacted by Britain's parliament, the child will be born a future king or queen in waiting.
The child will displace Prince Harry as the third in line to the throne, coming behind Queen Elizabeth's eldest, Prince Charles, and his son, Prince William.