A third baby whose DNA was edited as part of a series of 'monstrous' experiments by disgraced scientist He Jiankui may already have been born, experts fear.
Physician and ethicist William Hurlbut spoke out in January over revelations that He had altered the genes of a third embryo, expected to be born in June or July.
With June now behind us, Professor Hurlbut fears that the child may already have been delivered - or, if it hasn't, that China may decide to keep it quiet when it has.
'A normal birth is 38 to 42 weeks, and it’s pretty close to the center of that,' the Stanford University professor told MIT Technology Review.
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A third baby whose DNA was edited as part of a series of 'monstrous' experiments by disgraced scientist He Jiankui (left) may already have been born, experts fear. Stanford University physician William Hurlbut (right) broke the news about the pregnancy in January
'The gene editing occurred during IVF, or lab dish fertilisation.
'First, sperm was 'washed' to separate it from semen, the fluid where HIV can lurk.
'A single sperm was placed into a single egg to create an embryo.
'Then the gene editing tool was added.
'When the embryos were three to five days old, a few cells were removed and checked for editing.
'Couples could choose whether to use edited or unedited embryos for pregnancy attempts.
'In all, 16 of 22 embryos were edited, and 11 embryos were used in six implant attempts before the twin pregnancy was achieved.'
Professor Hurlbut is not alone in his fears, with some researchers predicting that the secretive Chinese regime will never announce the child's birth.
Given the controversy surrounding the announcement of the birth of the first two gene-edited infants in November 2018, that seems like a fairly safe bet.
Among the scientists raising their heads above the parapet on the issue is Rosario Isasi, a health and human rights lawyer at the University of Miami whose research and work focuses on the regulation of human genetic technologies.
Ms Isasi says she has been working to encourage scientists in China to speak out and limit the damage from the country's unethical human experimentation.
She fears that experts in the country are reluctant to speak out, however, and that Beijing is keen to avoid any further publicity over the issue.
'The government is extremely aware of any transgressions,' Ms Isasi said in an in-depth article by MIT Technology Review's Antonio Regalado.
'They have the Tiananmen anniversary, they have the Hong Kong protests, and they have the CRISPR babies.'
Pictured: He Jiankui speaks during an interview at a laboratory in Shenzhen in southern China's Guangdong province in October, 2018
Several scientists reviewed materials that Dr He provided to the AP and said tests so far are insufficient to say the editing worked or to rule out harm.
They also noted evidence that the editing was incomplete and that at least one twin appears to be a patchwork of cells with various changes.
'It's almost like not editing at all' if only some of certain cells were altered, because HIV infection can still occur, famed Harvard University geneticist Professor George Church said.
Church and Dr Kiran Musunuru, a University of Pennsylvania gene editing expert, questioned the decision to allow one of the embryos to be used in a pregnancy attempt, because the Chinese researchers said they knew in advance that both copies of the intended gene had not been altered.
'In that child, there really was almost nothing to be gained in terms of protection against HIV and yet you're exposing that child to all the unknown safety risks,' Dr Musunuru said.
The use of that embryo suggests that the researchers' 'main emphasis was on testing editing rather than avoiding this disease,' Church said.