He said he was "proud" of his work, and believed that he was helping people who otherwise would have no hope for life. The twins were born healthy this month in China, He said.

World-leading researchers at the summit who heard his account expressed deep concerns about the ethical risks and unpredictable possible outcomes of the experiment.

David Baltimore, chair of the summit's organizing committee, said it would be irresponsible to proceed with any genome editing at the clinical level unless and until the safety issues have been dealt with and there is universal consensus.

Baltimore said He's research was not transparent and shows a failure of self-regulation by the scientific community.

Robin Lovell-Badge, head of the Laboratory of Stem Cell Biology and Developmental Genetics at the Francis Crick Institute in the UK, said He was misguided and took bad advice.

In the talk, He said he had approached four other scientists in China and the United States to review the consent form he later gave to the parents. He said he also received feedback from scientists at meetings over the past few years.