TOKYO, Feb 23 (Reuters) Japanese Crown Prince Naruhito has welcomed his sister-in-law's pregnancy even though the birth of a boy would scuttle his daughter's chances of becoming the first reigning empress since the 18th century.
Plans to revise the imperial succession law to give women equal rights to inherit the throne were put on hold earlier this month after news that Princess Kiko, 39, the wife of the emperor's second son, was pregnant.
No males have been born in the royal family since 1965.
Conservatives hoping to maintain an imperial male line they say stretches back more than 2,000 years say the birth of a boy would at least postpone the need for the legal change.
At a news conference to mark his 46th birthday today, Naruhito said he and Crown Princess Masako were pleased by the news of Kiko's pregnancy and hoped that all would go well.
But he sidestepped comments on what this might mean for the succession and the future of his only child, 4-year-old Aiko.
''As a parent I have various thoughts, but I will refrain from commenting further,'' Naruhito said.
Though Japan's royals usually avoid controversial comments, Naruhito set off shock waves in May 2004 when he told a news conference that Masako, 42, a Harvard-educated former career diplomat, had exhausted herself trying to adapt to royal life.
Masako has been largely absent from public view due to a stress-related mental condition that royal watchers say was caused partly by pressure to bear a male heir.
MODERN DUTIES Naruhito said Masako was improving, but echoed a statement by her doctors last year urging that she be allowed to use skills developed before her marriage in her official duties.
Masako had hoped to act as a ''royal envoy'' after her marriage, but her travel has been restricted by court officials.
''I think it may be necessary to seriously consider what we can do in this age, what we can do because we are of this generation,'' Naruhito said.
The crown prince's younger brother, Akishino, has been critical of Masako's search for self-fulfillment, stressing royal commitment to duty instead.
Naruhito spoke tenderly of Aiko, who starts nursery school this spring, describing how she took a cake to her mother when Masako was in bed with a cold on her birthday last December.
He also said Aiko was fascinated with Japan's national sport of sumo, excitedly watching the giant wrestlers on TV and imitating their moves.
''She also knows the names of all the top wrestlers,'' the proud father added. ''I don't know nearly as much.'' A 1947 law limits the imperial succession to males who are descended from an emperor through the paternal line, but experts have said it is difficult to maintain the system given that the system of royal concubines no longer exists.
Opinion polls have shown that a majority of the public supports letting women ascend the throne and passing it to their children, although many also agree there is no need to rush through the legal revisions now that Princess Kiko is pregnant.
Reuters CS DB0944