Dr. He said the experiment worked for a couple whose twin girls were born in November. He said there were no adverse effects on other genes.

In a video that he posted, Dr. He said the father of the twins has a reason to live now that he has children, and that people with H.I.V. face severe discrimination in China.

Dr. He’s announcement was reported earlier by the MIT Technology Review and The Associated Press.

In an interview with the A.P. he indicated that he hoped to set an example to use genetic editing for valid reasons. “I feel a strong responsibility that it’s not just to make a first, but also make it an example,” he told the A.P. He added: “Society will decide what to do next.”

It is highly unusual for a scientist to announce a groundbreaking development without at least providing data that academic peers can review. Dr. He said he had gotten permission to do the work from t he ethics board of the hospital Shenzhen Harmonicare , but the hospital, in interviews with Chinese media, denied being involved. Cheng Zhen, the general manager of Shenzhen Harmonicare, has asked the police to investigate what they suspect are “fraudulent ethical review materials,” according to the Beijing News.

The university that Dr. He is attached to, the Southern University of Science and Technology, said Dr. He has been on no-pay leave since February and that the school of biology believed that his project “is a serious violation of academic ethics and academic norms,” according to the state-run Beijing News.

In a statement late on Monday, China’s national health commission said it has asked the health commission in southern Guangdong province to investigate Mr. He’s claims.

Many scientists in the United States were appalled by the developments.

“I think that’s completely insane,” said Shoukhrat Mitalipov, director of the Center for Embryonic Cell and Gene Therapy at Oregon Health and Science University. Dr. Mitalipov broke new ground last year by using gene editing to successfully remove a dangerous mutation from human embryos in a laboratory dish.