The hospital said it deeply regretted that the hoax call had been transferred to a ward in the early hours of Tuesday morning and a short conversation was held with one of the nursing staff.

The conversation included some general details of the duchess's condition and care, according to audio posted online by the DJs' Sydney-based radio station, 2Day FM.

2Day FM apologized Wednesday for a prank it said was "done with light-hearted intentions."

The duchess is not yet 12 weeks pregnant, Clarence House told CNN on Monday, so the palace is not announcing a due date for the child. Confirmation of the pregnancy followed months of speculation among royalty-watchers.

William and Catherine's child will be next in line to the British throne after William, regardless of whether it is a boy or a girl.

Planned changes to the law of succession that end the tradition of a boy taking precedence over an elder sister are already de facto in effect, the British Cabinet Office said.

William and Catherine were married at Westminster Abbey on April 29, 2011, in London's biggest royal wedding in three decades.

Their baby would be the first grandchild of Prince Charles and the late Diana, Princess of Wales.