BEIJING, March 27 -- Gazing upon her 6-month-year old son, Wang Lu, a mother of two, feels content, despite the looming challenge of registering her second child at the local household registration office.

Her first child was a girl, so Wang, 38, is pleased that her second child is a boy, as having both sons and daughters is considered a blessing in her hometown in southeast China's Fujian Province.

Still, she remains troubled because her son is considered"illegal" based on China's family planning policy. Because of the policy, she will have to pay a large sum of "social upbringing fees" before registering her son's permanent residence (or hukou in Chinese).

SOCIAL COST OF UPBRINGING

The social cost of upbringing is paid to offset the costs brought by any children forbidden under the family planning policy, as fostering a child consumes social resources and public services.

China is a country with a huge population but limited natural resources, unreasonable population growth would cause heavy burden on society and block the country's development, according to official documents on the policy.

"Social upbringing fees" are controversial in China, with the public and lawmakers constantly questioning where the fees go after collection.

In the past few decades, stories of family planning officials abusing their power have cropped up frequently. Stories of forced abortions for farmers or detention of the relatives of those who refused such abortions have circulated in Linyi city of east China's Shandong Province, according to family planning authorities who investigated such cases in 2005.

Illegal detention of those having a second child also occurred last year in Linyi. The novel of 59-year-old Nobel laureate Mo Yan,"Frog," depicts a rural obstetrician who carried out thousands of abortion operations to strictly implement the one-child policy. Mo's work is believed to be set in his hometown in Shandong's Gaomi.

The social upbringing fees are based on the family planning law and a State Council regulation, and procedures for collection should be according to law, Zhai Zhenwu, head of the China Population Association (CPA), was quoted as saying in an article carried by thepaper.cn on Friday.

Though the fees have been controversial, Zhai said "one has to abide by the law and cannot trample on it even if they are not satisfied with it."

Illegal detention is certainly not sanctioned by law and must be banned, Zhai said.

The role of social upbringing fees should not be negated due to extreme cases, he said.

It is very difficult to collect the social upbringing fees with only about 20 percent collected, he said, adding it is rare to see forced collection nowadays.

THE AMOUNT OF THE FEE

China's family planning policy was first introduced in the late1970s to rein in the surging population by limiting most urban couples to one child and most rural couples to two children, if the first child born was a girl. The policy was later relaxed, with its current form stipulating that one of the parents must be only child if the couple are to have a second child.

The policy was relaxed in order to deal with China's aging population, dwindling labor force and gender imbalance as parents' preference for sons has led to abortions of female fetuses.

China's labor force, aged from 15 to 59, decreased by 3.45 million year on year in 2012, marking the first "absolute decrease" since China's reform and opening up in 1979.

As of 2013, the number of Chinese people aged 60 or above exceeded 202 million, 8.53 million more than in 2012 and accounting for 15 percent of the total population.

But both Wang Lu and her husband are not only children in their respective families. which means under current policy, their second child is "illegal."

As the second child is six months old, Wang is pondering on her son's hukou. But first she has to know how much the family should pay the fee.

Chinese director Zhang Yimou and his wife paid a record seven million yuan (1.13 million U.S. dollars) in social upbringing fees in 2013 after admitting they violated the family planning policy by giving birth to three children.

Since then, public attention has been drawn on the amount of the fees. According to a State Council regulation promulgated in 2002, the social cost of upbringing is based on the per capita income in a region, parents' income and the circumstances involved concerning the violation of the birth control policy.

The sky-high fee paid by Zhang Yimou include fines for delayed payment. The regulation also stipulates that social upbringing fees and the overdue fines should be submitted to the national treasury.

Different places, even different districts in one city, mean different social cost of upbringing.

Wang Lu said her hukou was in Beijing's Chaoyang district, where the the capital's Central Business District locates, and her husband's hukou is in Changping district, a suburb in the north. The fee in Chaoyang could be two times that of Changping, which means a gap of about 180,000 yuan.

Wang said she could choose to register her son in Changping and pay around 200,000 yuan.

"I really want a boy, although I love my daughter very much," said Wang who got pregnant around the same time her daughter reached school age. She decided to give birth to the child and was expecting further policy changes, such as removal of fees for the second child, in the future.

Zhai, from the CPA, said the adjustment of the population policy is "an irresistible trend" and should be "safe and steady." He called for examination of China's population policy "under a historical background."

"Adjustment is only a matter of time," he said.