Tyrene White has never met Chen Guangcheng, the blind lawyer at the center of a rapidly evolving diplomatic dispute between the United States and China. But she knows that his revelations about the horrors of China's one-child policy - the work that got him tossed into prison - are absolutely accurate.

She's done a similar investigation herself.

White, an Asia specialist at Swarthmore College, is perhaps the foremost authority in the United States on China's birth-planning laws. She's conducted firsthand interviews and field research, and her writing on the topic includes the book China's Longest Campaign: Birth Planning in the People's Republic, 1949-2005.

"Every single thing he described in his report, every detail he described about how this occurred, the techniques that were used, were completely consistent with what I found," White said in an interview.

On Thursday, U.S. officials said the rights activist now wants to leave China, a reversal that follows his dramatic escape from house arrest and a six-day stay the American Embassy.

Chen's activism in opposition to the policy that generally limits couples to one offspring is sometimes overlooked in the news coverage surrounding his fate.

The law has altered millions of lives in China. In the countryside, the birth policy, coupled with a cultural preference for sons, long resulted in daughters being killed at birth or abandoned. Easily available ultrasound has led to the abortion of female fetuses.

It has also affected hundreds of thousands in the United States, where parents have adopted some 80,000 Chinese girls, most of them abandoned at birth and swept into state orphanages.

Since Chen did his research in 2005, White said, the birth policy has become more relaxed and its implementation more complex.

In cities, the official policy remains one child per couple - unless both husband and wife are only children. Then they can have a second child.

Today, more and more couples meet that standard, having been raised in one-child households.

The rural policy is more of a "one-son or two-child policy." If the first child is male, the parents can have no additional children. If the first is female, they can try later for a son.

"They still have the official policy in place," White said, but "the effect of that policy has been substantially undermined."

In 1978, Chinese officials decreed that only lower birthrates could prevent famine and foster economic development.

Enforcement has, in some cases, been horrendous. Chen documented that in Linyi, a town in Shandong province, tens of thousands of women underwent forced abortions and sterilizations. In 2005, more than 7,000 women there endured mandatory procedures, he found.

The next year, Chen was jailed for disrupting traffic and damaging property, serving four years before being released into house arrest with his wife, daughter, and mother.

White said that for ordinary Chinese, penalties for having "extra children" can be severe. Families may face heavy fines or lose their jobs. Their house might be knocked down.

At the same time, she noted, local officials face enforcement pressures. For them, failure to meet birth limits can mean lower pay and diminished career prospects.

White grew interested in the topic as a graduate student at Ohio State University in the late 1970s. The United States and China had normalized relations after decades of isolation and antagonism, and a professor discussed what the new birth law might portend.

"I was stunned," White said. "It struck me, as a young woman myself, what it would mean to have this policy imposed."

In those days, Chinese women had to undergo gynecological exams every three months to check for pregnancy. Married couples needed a birth permit before having a child. If they became pregnant without permission and the local quota was full, they could be forced to have an abortion.

For White, the professional later became personal: In the late 1990s she began the process of adopting a daughter from China, now 12.

Today she believes the one-child policy will disappear in her lifetime - altered to allow second and maybe third children.

One reason is the policy has pushed the sex ratio way out of balance. The natural ratio is 105 boys to 100 girls. In China, the figure is 118. The government says that by 2020, Chinese society will include 24 million bachelors who have little chance of finding a wife.

A second reason is that Chinese demographers are helping government leaders understand that a blunt policy is hard to reverse. Once fertility rates get low, they tend to stay that way.

A third is that the state-planning law makes coercion illegal - and China insists it is becoming ever more a country ruled by law.

"Over the course of the last decade," White said, "there has been a general effort to move closer to a posture more consistent with global norms."