BEIJING — The Year of the Pig has turned into the year of the baby.

Chinese hospitals have been submerged in recent months under a tide of pregnant women; newborns are arriving in droves; and companies that manufacture diapers are upping their advertising budgets.

The reason is simple: The Year of the Pig, which began Feb. 18, is a good year to be born.

Since time immemorial, prospective parents have been told, children born under the pig's patronage will benefit from the animal's image as fat, happy and prosperous. Now, couples who schemed to have their babies in these blessed times are hoping for good fortune.

"My family already has two pigs, including my father, and I want to add one more pig," said a pregnant 28-year-old Beijing secretary who identified herself only as Ms. Lian. "I guess three pigs will also bring luck to us," she explained. "Also, I believe people who are born in the Year of the Pig are honest, because my father is such a person."

The number of couples who calculated to have their babies in this auspicious year has provided a vivid reminder that, however fast China may be transforming its economy and merging with the modern world, the pull of an ancient culture has remained strong among its 1.3 billion people. Physicians say couples who planned to have their children during the Year of the Pig include well-educated urban professionals, as well as farmers' wives who might be expected to be more traditional.

The government's family planning department said it has not yet established a nationwide estimate for how many extra babies will be born in the Year of the Pig. But Beijing hospital officials surveying busy birthing and prenatal care wards predicted a 20 percent increase. Extrapolating that to the 16 million births recorded annually across China in recent years would mean a jump of about 3 million babies.

The birthrate has long been a carefully watched number in China, where the government enforces a one-child policy for most urban families. Premier Wen Jiabao recently declared that the sometimes controversial policy must continue to allow Chinese to benefit from economic progress. But Year of the Pig families did not appear to be contravening the rules — just choosing this year to have their babies.

In Chinese tradition, one of 12 animals is assigned as a patron for each year. Besides the pig, there is the dog, which held sway over 2006, and the monkey, snake, horse, dragon, sheep, rooster, mouse, ox, rabbit and tiger. Each animal is supposed to endow children born during its year with special characteristics.

The rush to have children born in the Year of the Pig has put sudden pressure on medical facilities, already strained in China's overburdened healthcare system. Zhang Weiyuan, deputy director of Beijing Obstetrics Hospital, said that about 600 pregnant women a day have been visiting for prenatal examinations and that the number of births is climbing steadily.

"It's really a burden for the hospital, and now we are discussing how to deal with it," Zhang said.