Rules are changing; programs are closing.

Back in 2006, Paul and Heather Peters began compiling the stack of paperwork required to adopt a baby from China. Now, finally, they're about to become parents - but not to a child from the Middle Kingdom.

Their daughter is coming to them through a different adoption process in a separate country, Taiwan.

The Cheltenham couple changed course as the waiting period in China stretched from one year to two years to indefinite. But it's not just China, long the world's largest adopter, that has been beset by uncertainty.

In the last three years, the once-stable universe of international adoption has turned upside down, as the countries that routinely sent thousands of children to U.S. homes have limited the pool of potential parents, reduced the number of children who may be available, or closed their programs entirely.

"The big ones have all fallen apart," said Heather Peters, director of human resources for Yoh Services L.L.C. in Philadelphia. "Vietnam's gone. Guatemala's gone. China might as well be gone."

That's pushing couples to consider less-established programs in smaller countries - a significant change in the way thousands of Americans have built their families during the last two decades.

In 2004, Americans adopted a record 22,884 children from overseas. Since then, the figure has been falling, last year to 17,438. That's a 24 percent drop.

One big factor: major alterations in programs operated by the "big three," China, Russia, and Guatemala, which routinely account for two-thirds of all foreign adoptions. Another: delay and complication caused by implementation of the Hague Adoption Convention, a new set of international regulations.

Countries that sign on to the treaty, becoming "Hague-compliant," agree to greater transparency aimed at ending corruption and child-trafficking. In the United States, only adoption agencies that are "Hague-accredited" can operate in Hague countries, now numbering more than 70.

"This is the consequence of people paying attention" - and that's a good thing, said Adam Pertman, executive director of the Evan B. Donaldson Adoption Institute in New York. But nations must embrace Hague "best-practice" rules as a means of moving children into families.

"The answer in the long term cannot be, 'Some things don't work, so these kids stay in orphanages,' " he said.

In Guatemala, long troubled by allegations of fraud, processing of new adoptions has stopped. Officials there plan to revamp adoption procedures to comply with Hague provisions, but it's unclear when that might occur.

Russia closed and then reopened its program - with a new, strict emphasis on the health of potential parents, and fewer children being adopted. In recent times, Russia routinely sent upward of 4,000 children a year to the United States, but last year that figure fell to 1,861.

In January, Russian leaders called for adoptions to the United States to be curtailed or halted, upset by the acquittal of a Washington-area father whose adopted son died of heatstroke after being left in a car.

South Korea, once a world adoption leader, also has reduced its numbers over time, and plans to end its program by 2015.

That altered landscape has driven some U.S. adoption agencies out of business, forced others to add new services, and led many to try to develop new programs in emerging countries.

Three weeks ago, Chinese Children Adoption International, a Colorado agency that for 14 years has handled strictly China adoptions, announced it was starting a program in Haiti, partnering with a Christian charity in Port-au-Prince.

"The days of having one or two big, strong programs are over," said Janet Mintzer, chief executive officer of Pearl S. Buck International in Perkasie, which works in China, Korea, and the Philippines.

Last year, Mintzer traveled to Nepal, a country the size of Arkansas, pinched between China and India, to secure an adoption license. She journeyed to Colombia, Ecuador, Costa Rica, and Mexico to explore possibilities there.

PSBI received Hague accreditation, key to securing its future in a competitive field. More than a dozen agencies were turned down, including Adoptions From the Heart in Wynnewood, which had to close some overseas programs as a result.

Adoptions From the Heart plans to appeal and, in the meantime, focus on domestic adoption. The agency also started an "embryo adoption" service, in which the unused embryos of women who have undergone in-vitro fertilization are implanted in others who hope to become pregnant.

"There's hardly any foreign [adoptions] to do, even if we could do them," executive director Maxine Chalker said. "We're hoping Vietnam will open. We're hoping China will pick up. . . . There are a lot of families that are now not going to be able to get children."

Why would someone choose to adopt from overseas?

One reason is the dearth of healthy babies available for adoption in the United States.

Greater access to birth control and abortion, coupled with a lessening of the stigma once associated with single motherhood, has resulted in the placement of far fewer children. Traditional adoptions number about 13,000 annually, down from 89,000 in the mid-1970s.

A second big reason: certainty.

A couple who seeks to adopt domestically doesn't know if the wait for a child will last five weeks or five years. Some come away brokenhearted when a birth mother changes her mind at the last minute, or a birth father asserts his parental rights after everything seemed settled.

Overseas adoption requires extensive paperwork, significant expense, and untold investment of time, but prospective parents know that they will be matched with a child. And, until recently, they knew the timetable.

"You hang your hat on that, and you hang your heart on that," said Paul Peters, a Philadelphia lawyer.

Now that reliability has eroded.

Between 1989 and 2008, China sent 71,403 children to the United States, almost all of them girls who were living in state-run orphanages. That was more than from any other country.

Prospective parents flocked to what was the world's most efficient system, attracted to a centralized program with relatively liberal requirements.

Most of all, people were drawn to China because they knew why children were available: China's one-child policy, which results in the abandonment of baby girls.

But even as it grew in popularity, China's program began to slow. In 2006, the number of children adopted from China dropped after four straight years of growth. People speculated that the delay was deliberate, that in the lead-up to the Beijing Olympics, China didn't want to be seen as unable to care for its own.

New regulations banned adoptions by single people, by those older than 50, by anyone taking medicine for depression.

Meanwhile, experts say, demographic shifts in China have reduced the number of children who can be adopted. Rising prosperity has allowed more parents to pay the fine for having a second child. Domestic adoption has grown. And evolving attitudes about girls might be leading some parents to keep their daughters.

In 2005, 7,906 Chinese children came to these shores. Last year, the number was half that.

If you have spent several years preparing to adopt a girl from China, it's hard to turn away and embrace the idea of, say, adopting a boy from Kazakhstan.

For years, Heather and Paul Peters, both 32, devoted themselves to learning about China, reading books, attending cultural events, and talking to adoptive families. Heather even took night classes in Mandarin. But the waiting period kept lengthening.

"I thought the wait was going to get worse and worse," Paul Peters said.

He was right. By tracking the pace of China adoptions, they realized that the wait would last two years or more. They applied to Taiwan, which last year sent 267 children here.

In October, nine months after being placed on the waiting list, they were matched with a baby girl named Hsin-Hua Lin, born in the city of Chiayi, in southwest Taiwan.

A court ruling on the adoption is expected this month or next, and the Peterses could travel to Taiwan about a month later. They plan to name their daughter Olivia Hsin-Hua Lin Peters.

"You almost have this feeling of 'I'll believe she's mine when I'm actually holding her,' " Heather Peters said. "I wish I'd known about the Taiwan program first, because I would have skipped China."