"Everything's not closing down, but there's no question there's a constriction happening," said Adam Pertman, author of "Adoption Nation: How The Adoption Revolution Is Transforming America" and executive director of the Evan B. Donaldson Adoption Institute, a research organization. "I haven't seen anything like this in 15 to 20 years."

Tom DeFilipo, president of the Joint Council on International Children's Services, which represents international adoption agencies, said that for the first time in his organization's 35-year history, there are more U.S. families willing to adopt children than there are children legally available for adoption. "This is a transformational period for international adoption," DeFilipo said, "there's no question about it."

Vietnam is the most recent country to pull back on adoptions, announcing last week that it will close it doors to U.S. adopters once an agreement with Washington expires on Sept. 1. Vietnam shut down temporarily in 2003, after allegations of corruption and baby selling plagued its program, then reopened in 2005 to a rush of new adoptions.

Vietnam's announcement came after the U.S. embassy in Hanoi released a report detailing new corruption allegations, and citing a suspiciously high number of children listed as abandoned, which makes it impossible to prove they were truly orphaned or that their parents knowingly agreed to relinquish them.

But the very popularity of international adoption also drew greater scrutiny to its practices and abuses, as wealthy Americans and foreigners descended on impoverished countries with available children, paying fees that could reach $30,000 or more -- money that sometimes wound up in the pockets of corrupt local officials and adoption facilitators rather than orphanages in need.

The Vietnamese government strongly denied the accusations, saying it will shut down rather than deal with what it described as disrespectful U.S. officials. The two countries remain at an impasse.

Guatemala, also a popular county for U.S. adoptions, said on Tuesday that it would suspend the adoptions of 2,300 children by U.S. citizens for at least a month to investigate whether they were handled legitimately. On April 1, the State Department announced a total halt to new adoptions in Guatemala, as its government works to address longstanding problems with corruption and charges that women were enticed to put their children up for adoption for money.

Other countries are changing their policies for different reasons. China may deny travel permission for adoptions during the Olympics this summer because of traffic congestion, and waiting times to adopt children has increased from nine months to more than two years. In recent years China has moved to limit the type of families who can adopt, excluding from its program single parents and people who are obese or take anti-depressants.

Russia is working to encourage domestic adoption, and last year, for the first time since it opened its doors to foreign adoptions, more Russian children were adopted domestically than internationally, DeFilipo said. Korea -- the trailblazer of international adoption after poverty engulfed the country in the aftermath of the Korean War -- also has fewer children available for adoption as it has grown more prosperous and has encouraged Korean families to adopt.

As a result of all the cultural changes, restrictions and shutdowns, international adoption began to decline beginning in 2005, and its numbers are expected to keep falling, Pertman said. Adoptions had grown from 7,000 annually in 1990 to a peak of almost 23,000 in 2004, with Americans accounting for about half of all adoptions worldwide. The total fell to 19,411 in 2007. Last year, despite declining adoptions, China still ranked as the top country for adoptions, followed by Guatemala and Russia.

The influx of adoptees comprised the "revolution" that Pertman spoke of: playgroups for children from Asia, families with a mix of biological children and babies from overseas, culture camps to connect children with the heritage of their countries and the greater acceptance and high visibility of adoptive families. Celebrity adoptions only fueled the popularity, with New York magazine declaring blended families with children adopted internationally hip and trendy, thereby offending many adopters.

But the very popularity of international adoption also drew greater scrutiny to its practices and abuses, as wealthy Americans and foreigners descended on impoverished countries with available children, paying fees that could reach $30,000 or more -- money that sometimes wound up in the pockets of corrupt local officials and adoption facilitators rather than orphanages in need.

Adoptions ended in Cambodia after numerous scandals, some involving birth mothers placing their children temporarily in orphanages so they could be fed and cared for, then returning to find them "adopted" by foreigners. The Irish Independent in 2006 caught on tape a Vietnamese-American facilitator talking about how she forged birth certificates, paid off local officials and passed off children with parents as abandoned in order to put them up for adoption. She grossed $1 million for handling 150 adoptions.

To Pertman, international adoption is now at a turning point. The next phase of the adoption revolution, he believes, will be smaller countries with fewer children opening up to adoptions, like Ethiopia, while larger countries begin cutting back. He predicts fewer international adoptions, and more adoptions domestically of children in foster care.

he scrutiny, Pertman explains, is a natural part of the growth of international adoption and the process of moving to its next phase.

"We want to get adoption to the point where it's as ethical, as thoughtful, as humane and as efficient as we can make it," he said. "We want to make sure that adoptions are done right, and done for the right reasons, because kids need homes. We want to see that adoption is done not because demand drives the process, but because the need drives the process."

The changing nature of international adoption can be for the good, as agencies open programs in countries where they haven't been before, DeFilipo said. Ethiopia has grown in popularity as an adoption source, and other countries in Africa, Latin America and parts of Asia are considering programs.

But the world still has 143 million orphans, and the fact that so few are available for adoption "is a tragedy for the kids," he said.

That reality is likely to prompt more international disputes like the one in Vietnam.

DeFilipo's group and other adoption advocates are launching a campaign next week to pressure the State Department to settle its dispute with Vietnam and restart adoptions. He pointed out that Washington said last December, prior to the embassy report, that it planned to end the adoption agreement with Vietnam. Then it turned around last week and leaked the report about corruption to the press.

He and other advocates contend the State Department is bullying Vietnam and shutting down all adoptions, when it could work instead to end the abuses while allowing legitimate adoptions to continue. Vietnam remains open for adoptions from other countries.

"What the U.S. is doing is just another example of 'The Ugly American,'" DeFilipo said.

He's not the only one pointing the finger at the State Department. Thomas Atwood, president of the National Council for Adoption, an advocacy group, contended that frequent turnover among State Department staffers assigned to adoptions is behind some of the problems.

In Vietnam, staff come and go every two to three years, and officials don't understand the psychology and culture of adoptions, he said. A woman might list her child as abandoned on paperwork out of shame, not because the adoption is tainted. "They'll go through the paperwork and find something nefarious there when it's not," Atwood said.

The State Department has said it stands by its findings. Steve Royster, spokesman for consular affairs, said it's just not true that the U.S. government opposes adoption in Vietnam, or that it opposes international adoption in general.

The U.S. is working closely with countries to comply with the Hague Convention, an international adoption treaty aimed at reforming adoptions and ending abuses. Royster said the Hague agreement will put all countries "on the same page" when it comes to adoption rules and regulations, making the whole process more uniform and less vulnerable to exploitation.

"We're fully committed to international adoption when it's the best way to get families for these kids," he said.