Pregnancy Could Calm Male Heir Worries in Japan

For several years, Japan's royal family has been facing an Armageddon of sorts. Ancient tradition and an imperial succession law mandate that only males ascend to the throne, but Japan's royals are running out of males.

Now comes word of a new royal pregnancy that could save the male-only tradition, just as the Japanese were getting used to the idea of an empress -- specifically 4-year-old Princess Aiko, the only child of Crown Prince Naruhito and Princess Masako.

With no boys born to Japan's imperial family in a half-century, royal scholars had repeatedly warned that the future of the monarchy was at stake.

"No male heir produced by the crown princess. I think that's a big crisis," said Toshiko Marks, professor of multicultural understanding at Shumei University.

Japan's popular Prime Minister Koizumi promised he would push through changes to the Royal Succession Law and finally bring sexual equality to the monarchy.

Debate Over Monarchy's Future

The majority of Japanese voters liked the idea, but hard-core nationalists were furious.

Changes to royal traditions, they argued, would amount to treason against Japanese culture.

But just as it seemed their battle was lost with the law about to be changed, a stunning announcement came from the palace: Princess Kiko, the 39-year-old wife of the emperor's second son, is pregnant.

Plans to change the law evaporated right before Koizumi's eyes, as he was given word during a session of Parliament.

With this unexpected pregnancy, one could feel the sudden shift in public opinion. With the birth of a boy, the royal traditions could be saved.

Conservatives are calling it an act of the gods, and they are praying hard.

The birth of a boy behind the palace walls would ensure a male imperial line for another half-century or so. But what happens if Princess Kiko gives birth to another girl?

Well, little Princess Aiko is still practicing that royal wave, just in case the Chrysanthemum Throne is hers to claim someday.

ABC News' Mark Litke filed this report.