Chinese scientist He Jiankui shocked the scientific community after revealing that he had successfully altered the DNA of twin girls born in November 2018 to prevent them from contracting HIV.
The second woman carrying a gene-edited foetus in China could now be 12 to 14 weeks into her pregnancy, according to a US physician who is in close contact with Chinese scientist Jiankui.
State media reported on Monday that a preliminary investigation confirmed that a second woman became pregnant and that she will be put under medical observation, but no other details about her are known.
Professor He, who now faces a police investigation, had mentioned the potential second pregnancy at a human genome conference in Hong Kong in late November, but its status was unclear until now.
William Hurlbut, a physician and bioethicist at Stanford university in California who has known He for two years, told AFP it was "too early" at the time for the foetus to appear on an ultrasound.
Based on extensive conversations with He, Hurlbut said: "I get the impression the baby was fairly young when the conference happened. It could only be detected chemically, not clinically (at the time).
"So it could be no more than four to six weeks old (at the time), so now it could be about 12 to 14 weeks." Hurlbut said he met He at a scientific conference co-chaired by Hulburt two years ago. Since then the pair have met at least four times during He's visits to Stanford.
Hurlbut added he was not involved in He's project in any capacity, and only knows about the second pregnancy from what He has told him.
Wang Haoyi, a Development Biologist at the Chinese Academy of Sciences, told AFP that the experiment's effects on the health of the twin babies is hard to predict, but that their identities should be protected to give them the best chance of a normal life.
"I think we definitely need to take serious measures to protect their privacy," he said.
"We don't even need to let them know that they are any different from others."
Hurlbut said he had planned to visit He's lab following the genome summit.
But after news of his experiment was published, He was placed "under protection of security people" and the two have not seen each other in person, he said.
They exchanged emails and spoke on the phone every week after that, but Hurlbut last heard from He seven days ago.
He has been residing in an apartment at the Southern University of Science and Technology (SUSTech) in the city of Shenzhen, where his family has been allowed to visit him in the day time, Hurlbut said.
"He doesn't sound like a person under terrible fear or stress." said Hurlbut.
"He said he was free to go out on to the campus and walk around." But He could be facing legal trouble.
Fan Chen, a Beijing-based lawyer, told AFP that He could face up to three years imprisonment for forging research papers.
But Si Weijiang, a Shanghai-based lawyer, said He could face harsher penalties.
Authorities could prosecute him for on endangering public security or medical malpractice "but ... these laws have never been applied to such acts", Si added.
A probe by the Guangdong provincial government found that He had "forged ethical review papers" and "deliberately evaded supervision", according to state-run Xinhua news agency.
He had "privately" organised a project team that included foreign staff, it said.
He will be "dealt with seriously according to the law," and his case will be "handed over to public security organs for handling", Xinhua said.