NEW YORK - After tripling over the past 15 years, the number of foreign children adopted by Americans dropped sharply in 2006, the result of multiple factors which have jolted adoption advocates and prompted many would-be adoptive parents to reconsider their options.

The consequences could be profound for the ever-growing numbers of Americans interested in adopting abroad. Already, some have had their hopes quashed by tightened eligibility rules in China; adoptions from Africa, where millions of children have been orphaned by AIDS and wars, could increase if those from China and Eastern Europe continue to decrease.

Declines were recorded last year in nearly all countries that recently have been the top sources of adopted children - China, Russia, South Korea and Ukraine among them. Increases from less familiar alternatives - Ethiopia, Liberia, Haiti and Vietnam - partly offset the drop, but some experts believe the era of constantly surging foreign adoption has ended.