Japan's Princess Kiko is pregnant, media reports said on Tuesday, raising the possibility of a male heir for the imperial family just as parliament is planning to debate whether women should be allowed to inherit the throne.
No boys have been born into the imperial family since 1965, when Kiko's husband, Prince Akishino, the second son of Emperor Akihito, 72, was born. The current law allows only males descended from emperors to become sovereign.

Japan's top government spokesman Shinzo Abe said the government could not confirm the pregnancy, but added that the Imperial Household Agency, which handles royal affairs, might make an announcement regarding the reports by the end of the day.

If confirmed, the pregnancy is likely to boost conservative opposition to revising Japan's imperial succession law to let women inherit the throne, legislation Prime Minister Junichiro Koizumi has said he wants to enact in the current session of parliament ending in June.

"I will still submit the law (for the revision) ... during the current session of parliament," Koizumi told a parliamentary panel after the news broke, adding that it would be difficult to preserve a stable succession if only males could reign.

But Katsuya Okada, former head of the main opposition Democratic Party, said in the same panel: "I'm not saying we should consider this for 5 or 10 years. But I do feel there's something strange about passing it during this session of parliament."

Crown Prince Naruhito and his wife, Masako, have one child, the 4-year-old Princess Aiko. Masako, 42, has been unable to perform most of her official duties for more than two years due to a mental disorder caused by the stress of adapting to rigid royal life, including, royal watchers say, pressure to bear a son.

Those opposed to changing the succession law want to maintain a male line they say stretches back more than 2,000 years and analysts said the news would bolster the argument -- echoed by some members of Koizumi's cabinet -- that there is no reason to rush to legislate revisions.

"There were already a lot of people who were cautious (about revising the law). They don't mind a female empress but do not want her to pass on the throne to her children," said Yasunori Sone, professor at Keio University in Tokyo.

"Now, the baby could be a boy and those who advise caution and say there is no need to rush will grow in number."

Under the current law, if the newborn is a boy, he would be third in line to inherit the Chrysanthemum throne after his father and Crown Prince Naruhito.

Both of Kiko's two children are daughters.

Kyodo news agency said the 39-year-old princess would likely give birth in September or October.

Conservatives have promoted the idea of reviving princely houses abolished after World War Two or even resuming the custom of royal concubines in an attempt to widen the potential pool of male heirs.

"Very frankly, before there was a system in which the emperor could have several wives," Yoichi Masuzoe, a lawmaker with Koizumi's ruling party, said before the news reports.

"This was the safety valve to keep the masculine line, but today it is impossible," added Masuzoe, who is in favor of changing the succession law.

Some officials at the Imperial Household Agency have said in the past that they were pinning their hopes on Kiko and Akishino having a third child that would be a boy.

If the succession bill is passed, Aiko would eventually become Japan's first reigning empress since the 18th century.

Japan has had eight reigning empresses, but traditionalists stress that none of the female rulers passed on the throne to children who were not heirs of an emperor.

The reports of the pregnancy even affected the stock market, boosting share prices of makers of baby care goods Pigeon Corp., which rose 5.7 percent to 1,777 yen, and Combi Corp., which climbed 9 percent to 850 yen.