Because her 15-month-old son has a US passport, the law does not allow him to be registered in his mother's area of residence, which means he will not be automatically admitted to Chinese public schools in the area. Wu will have to register him as a foreigner and pay an extra fee accordingly.

His access to public health care will also be problematic, as China's public health care system is tied to urban household registration. Wu's son is not allowed to register as a Shanghai resident, which will make it more difficult for him to obtain local education and health care.

The family must return to the US regularly -- once every two years -- until the child is 18 in order to maintain his US nationality. Dual nationality is prohibited under Chinese law.

The US Embassy in China said that if a child obtains urban household registration in China, he or she will be considered to have given up their US nationality.

Zhang Youde, dean of the social science department at the Shanghai University of Political Science and Law, said the phenomenon could lead to the loss of China's "elite."

"US citizenship has attracted some Chinese parents due to advantages related to education and welfare, similar to Chinese who made great efforts to obtain urban residence in times past," Zhang said.

Others have chosen to give birth abroad in order to sidestep China's one-child policy, exposing a loophole that allows the wealthy to ignore the law while still impacting society, Zhang said.

However, Wang Daben, an associate professor at the population research institute of East China Normal University, said the choice should be left up to the individual.

"There is no need for China's government to interfere. It is up to the US government to decide whether to control the phenomenon or not," Wang said, adding that there have been some calls in the US to make changes to the country's immigration policies.

"Human nature shows that people are most likely to choose the option that maximizes self-interest," Zhang said, adding that efforts must be made to change China's social environment in order to reduce the number of Chinese births that occur overseas.

Children born in the US to parents of a differing nationality are given until the age of 18 to choose their nationality.

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