When Hu married a construction worker seven years ago, she knew she was going to have only one child, although the area where she lives, the Jiuquan region in northwestern Gansu province, is one of the rare places in China where those living in rural areas have been free to have two children since 1985.

"Those people with two children are those who are better off," said Hu, 32, dropping her six-year-old son off at kindergarten. "The majority of people in my village only have one child."

Advocates of reforming China's one-child policy use Hu and millions like her as evidence that relaxing the law will not lead to a surge of births in the world's most populous nation.