“ADOPTION is bittersweet,” said Susan Soon-Keum Cox, vice president for public policy and external affairs at Holt International, a Christian adoption agency based in Eugene, Ore., with an extensive program in China. The process connects birth parents, child and adoptive parents in an unequal relationship in which each party has different needs and different leverage. It begins in loss.

Adoptive parents and adoption agencies have powerful incentives not to talk about trafficking or to question whether a child was given up voluntarily, especially given how difficult it is to know for certain. Such talk can unsettle the children or anger the Chinese government, which might limit the families’ future access to the country or add restrictions to future adoptions. And the possible answer is one that no parent wants to hear.

Most parents contacted for this article declined to comment or agreed to speak only on the condition of anonymity. Several said they never discussed trafficking, even with other adoptive parents. To a query from The New York Times posted on a Web forum for adoptive parents, one parent urged silence, writing, “The more we put China child trafficking out there, the more chances your child has to encounter a schoolmate saying, ‘Oh, were you stolen from your bio family?’ ”

Such reticence infuriates people like Karen Moline, a New York writer and a board member of the nonprofit advocacy group Parents for Ethical Adoption Reform, who adopted a boy from Vietnam 10 years ago. “If the government is utterly corrupt, and you have to take an orphanage a donation in hundred-dollar bills, why would you think the program was ethical?” she said. “Ask a typical Chinese adoptive parent that question, and they’ll say, my agency said so. My agency is ethical. People say, the paperwork says X; the paperwork is legitimate. But you have no idea where your money goes.

“Now you have to give $5,000 as an orphanage fee in China. Multiply that by how many thousand adoptions. Tens of millions of dollars have flowed out of this country to get kids, and you have no accounting for it.”

Agencies say that cases of child abduction are few compared with the number of abandoned Chinese babies who found good homes in America. The abductions reported in August were of 16 or more children taken from their parents between 1999 and 2006. According to the investigation, population-control officials threatened towering fines for couples who violated the one-child policy because they were too young to be married or already had a child, or because they had themselves adopted the child without proper paperwork. When the parents could not pay, the officials seized the children and sent them into the lucrative foreign adoption system.