He Jiankui, the Chinese scientist who stunned the world by announcing the birth of two CRISPR-edited twins this week, has claimed that a second woman is pregnant with a another CRISPR baby.

Jiankui, whose work has been condemned by Chinese peers and the Shenzhen City Medical Ethics Expert Board, made his announcement on the second day of the international gene-editing summit in Hong Kong. On stage he said he was “proud” to have edited the genes of the two twin girls to make them HIV-resistant, as an HIV vaccine is not currently available.

Audience members were critical. Nobel laureate David Baltimore said continuing with the experiment was irresponsible, and argued for much greater transparency: “I think there has been a failure of self-regulation by the scientific community because of the lack of transparency”, he noted.