San Diego ? More than 30 years after the world greeted its first “test-tube” baby with a mixture of awe, elation and concern, researchers say they are finding only a few medical differences between these children and kids conceived in the traditional way.

More than 3 million children have been born worldwide as a result of what is called assisted reproductive technology, and injecting sperm into the egg outside the human body now accounts for about 4 percent of live births, researchers reported Sunday at the annual meeting of the American Association for the Advancement of Science.

The majority of assisted reproduction children are healthy and normal, according to researchers who have studied them.