The baby will be third in line for the British throne, and should eventually succeed grandfather Charles and father William as king or queen of Britain and 15 other countries including Canada and Australia.
But little else is known about the eagerly awaited royal baby, from how it will arrive to its gender or its name.
Kate - formally known as the Duchess of Cambridge - is expected to deliver in the private Lindo Wing of the hospital, where Princess Diana gave birth to William and his younger brother, Prince Harry. It is not clear if she will have a natural birth or deliver by a planned cesarean section.
