The Crown Princess will be absent from today's funeral ceremony for the Empress Dowager and related events that will run until Wednesday, the Imperial Household Agency said Monday.
Agency officials said poor health will prevent the Crown Princess from attending the functions.
Grand Master of the Crown Prince's Household Kiyoshi Furukawa said the Crown Princess will miss the events because she is suffering from tiredness, partly caused by the summer heat.
He said pregnancy was not the cause of the cancellation.
The Crown Princess was confirmed pregnant in December 1999 but miscarried later that month.
It has been speculated that a variety of modern medical measures have been taken to assist the Crown Princess to conceive.
The Shinto-style funeral ceremony for the Empress Dowager will be held this morning in Tokyo's Bunkyo Ward, followed by another ceremony at the Musashino Imperial Mausoleum in Hachioji, western Tokyo, where a mausoleum for the Empress Dowager will be built.
Members of the Imperial Family and other dignitaries, including Prime Minister Yoshiro Mori, are expected to attend the ceremony.
The Empress Dowager, wife of the late Emperor Hirohito, died of old age on June 16 at age 97. Her posthumous title is Empress Kojun.