Analysts say China's population would have hit 1.6 billion people today instead of the actual 1.3 billion if it were not for the Communist government's Planned Birth policy implemented since 1979. However, as effective as the policy has been, It remains controversial - raising enormous human rights questions in the way it is carried out.

Chinese mothers play with their children on a frozen lake in Beijing

The policy generally restricts couples in urban areas to one child. Rural dwellers, Muslims and members of other ethnic minorities are allowed two or three.

Implementation of the birth control policy is uneven and sporadic, however, with townships deciding if and how to enforce the rules. Observers say this practice has resulted in abuses by local officials, who have forced women to undergo abortions after getting pregnant more times than the state allows.

One case that has sparked international attention is in Eastern China's Shandong province, where authorities have jailed Chen Guangchen. Chen - who is blind - is a self-taught lawyer, who has investigated the cases of and argued on behalf of women in the province who were tortured, forced to undergo abortions or sterilized against their will.

Defending him is Teng Biao, a Beijing lawyer who - with Chen - investigated the cases.

"Some of the women were in poor health and were not fit to undergo the procedures," he explained. "Some were forced to abort two or three days before they were scheduled to give birth."

Teng says he does not oppose the birth control laws themselves, which he says give women the right to choose whether or not to be sterilized.

Poster at a hospital in Beijing reminds parents that sex-selective abortions are illegal

One indirect result of the one-child policy is the shrinking number of Chinese females compared to males.

In a culture that, since ancient times, has prized male offspring - one result of the birth control policy has been that families have opted for their one child to be a boy. This has created what experts say is a gender ratio disparity of 117 male births to 100 female births - far above the approximately 108 -100 that is considered natural.

The Chinese government has in recent years sought to reverse this trend by banning sex selective abortions, and embarking on a publicity campaign to encourage parents to appreciate having girls.