Teresa Heinz Kerry, 74, has been moved to a Boston hospital from the Nantucket Cottage Hospital, where she was initially admitted on Sunday.
John Kerry, the veteran American politician and 2004 presidential candidate, has been sworn in as the United States secretary of state, replacing Hillary Clinton.
Heinz Kerry grabbed headlines at the start of the convention after telling a reporter to "shove it" when he questioned her about a speech she had given.