Communist Party leaders have praised their one-child policy for preventing the population from spiraling out of control, but critics say it has spawned decades of forced abortions, infanticide and child trafficking.

China, the world's most populous country with nearly 1.4 billion people, says the policy has averted 400 million births since 1980, saving scarce food resources and helping to pull families out of poverty.

Critics say it has created a generation of spoilt brats and re-enforced a cultural preference for male heirs who can better take care of their parents in old age — if couples are allowed only one child, many want to make sure it is a boy.