Crown Prince Naruhito of Japan has said his wife, Princess Masako, is exhausted from the pressures of royal life.
By Jonathan Head
BBC correspondent in Tokyo
In comments made on his 44th birthday on Monday, the heir to the Japanese throne said the princess was suffering from the accumulated burdens of motherhood, her official duties and the relentless pressure to produce a second, male child.
Last December Princess Masako was hospitalised after an attack of shingles brought on by stress.
Crown Princess Masako (R) is under pressure to produce a male heir
In carefully-phrased comments made last Thursday but released on Monday, Crown Prince Naruhito made it clear his wife is still finding it difficult to cope with the strain of life in Japan's formal and secluded royal family.
Amid her official duties and child rearing, and the effort of addressing the media's demands, he said, her exhaustion had accumulated.
Princess Masako has not appeared in public since she picked up shingles in December. It is a painful condition commonly brought about by stress.
Only males can ascend the Japanese throne
If Prince Naruhito died without a male heir, his brother, Prince Akishino, succeeds
But he has no sons either
One of the problems is the desire of the Crown Prince and Princess to raise their two year-old daughter, Aiko, in as normal an environment as possible.
The rigid etiquette surrounding the Imperial Household makes it almost impossible for the family to go outside the palace except on formal occasions.
Princess Masako had a successful career in the Foreign Ministry before her marriage and she has found it hard to adjust to the restrictions imposed by her royal status.
The Crown Prince said she was also feeling the pressure to produce a male heir.
Under Japanese custom only men can ascend the throne.
Continuing the line
Princess Masako suffered a miscarriage in 1999 and the media were ordered to curb their speculation during her second pregnancy.
The lack of a male heir to succeed Crown Prince Naruhito has prompted some politicians to suggest changing the rules to allow a female to succeed to the throne.
But the government is reluctant to start a debate which might call the very existence of the monarchy into question.
Under Japan's post-World War II constitution the Emperor has no political power but the institution is still venerated by many Japanese.