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.

Part of the reason he went ahead, He said, was his observation of earlier public survey and study results in the United States and the United Kingdom indicating a majority in society seemed to find the idea acceptable.

Lovell-Badge said He failed to do research in a properly controlled and careful manner, including publishing findings along the way and involving authorities in making decisions whether to go further.

The process of obtaining patients' informed consent was poorly executed, Lovell-Badge said.

Wei Wensheng, a professor at Peking University, asked He why he chose to cross a red line by performing clinical trials in secret.

That red line－the international consensus on prohibiting genome editing on germlines, which can pass on their genetic material to offspring－has been observed by the Chinese science community since the first human genome editing summit in 2015.

In response, He said he had consulted several institutions for feedback.

Many technical questions were raised about the necessity and authenticity of He's experiment.

David Liu from Harvard University questioned He on the unmet medical need of the experiment. Liu said an HIV-positive father and an HIV-negative mother already have a high possibility of having an HIV-free baby after "sperm washing", an effective technique that separates sperm from infected cells before fertilization to ensure the virus isn't transmitted. During the talk, He said he had performed the procedure in the experiment.

Some scientists also voiced concerns over the backlash of He's experiment on gene editing technologies worldwide.

"I feel more disturbed now," said Liu, who is also associated with MIT's Broad Institute and is the inventor of a variation of the gene editing tool. "It's an appalling example of what not to do about a promising technology that has great potential to benefit society. I hope it never happens again," he was quoted as saying by the Associated Press on Wednesday.