TOKYO — Japan’s Princess Kiko gave birth to a boy early today, providing the centuries-old Chrysanthemum Throne with its first male heir in more than 40 years, the palace announced.

The birth came about an hour after Kiko, 39, was reported to have undergone a Caesarean section. The boy is the third in line to the throne, after Crown Prince Naruhito and Kiko’s husband, Prince Akishino.

The arrival of a royal boy forestalled a looming succession crisis for the royal family.Japan’s 1947 succession law allows only males to ascend the throne, and prior to today, Naruhito and Akaishino were the only royals eligible for the crown.

The boy, the first male heir born in Japan since Akishino in 1965, was born at 8:27 a.m. and weighed 5.64 pounds, the Imperial Household Agency said. Kyodo News agency reported mother and child were in good condition.

Kiko, who already had two daughters, was hospitalized on August 16 after showing symptoms of partial placenta previa, in which part of the placenta drops too low in the uterus.

The gender of the baby had been a closely guarded palace secret, though Japanese tabloids had speculated the child would be a boy. The last potential male heir born was Akishino himself in 1965.

Emperor Akihito’s eldest son, Naruhito, has a daughter with his wife Masako, but the couple have no sons, meaning no one would have inherited the throne after he and his brother.

The looming succession crunch had prompted serious discussion of changing the law to allow a female to assume the throne.