(CNN) - A Chinese scientist who helped create the world's first gene-edited babies has been sentenced to three years in prison.

He Jiankui shocked the world in 2018 when he announced that twin girls Lulu and Nana had been born with modified DNA to make them resistant to HIV, which he had managed using the gene-editing tool CRISPR-Cas9 before birth.

He, an associate professor at the Southern University of Science and Technology in Shenzhen, said at the time that he was "proud" of the achievement. He later claimed that a second woman was pregnant as a result of his research.

But he was condemned by many of his peers, with the experiment labeled "monstrous," "unethical," and a "huge blow" to the reputation of Chinese biomedical research. Many people within the scientific community raised ethical concerns, including the level of consent He had obtained from the parents of the babies, and the level of transparency around gene editing.

On Monday, the Shenzhen Nanshan District People's Court sentenced He to three years behind bars and a 3 million yuan ($430,000) fine, China's state-run news agency Xinhua reported.

According to the court's findings, He became aware of potential economic gains from human embryo gene-editing technology in 2016, Xinhua reported. He worked with two medical researchers, Zhang Renli and Qin Jinzhou, to use gene-editing technology to produce babies that were resistant to HIV.

"The court held that the three defendants failed to obtain a doctor's qualification and pursued profit, deliberately violated the relevant national regulations on scientific research and medical management, crossed the bottom line of scientific and medical ethics, and rashly applied gene-editing technology to human-assisted reproductive medicine, and disrupted the medical treatment," Xinhua reported. "The nature of their behavior is serious and has constituted the crime of illegal medical practice."

Zhang was sentenced to two years in prison and fined 1 million yuan ($143,000), while Qin was given a suspended sentence of one year and six months in prison and fined 500,000 yuan ($71,600). According to Xinhua, all three defendants pleaded guilty in trials that were closed to the public to protect individual privacy.

All three defendants have reportedly also been banned from engaging in human-assisted reproductive technology services for life.

Editing the genes of embryos intended for pregnancy is banned in many countries, including the United States. In the United Kingdom, embryos can only be edited for research purposes with strict regulatory approval. It is unknown whether the procedure is safe or, if used in pregnancy, whether it can have unintended consequences for the babies later in life or for future generations.

In January this year, investigators from Guangdong Province Health Commission said that He had conducted the work "in pursuit of personal fame and fortune, with self-raised funds and deliberate evasion of supervision and private recruitment of related personnel." The authorities also said He forged ethical review documents and blood tests to circumvent a ban on assisted reproduction for HIV-positive patients.

China has invested heavily in gene-editing technology, with the government bankrolling research into a number of world "firsts," including the first use of the gene-editing tool CRISPR-Cas9 in humans in 2016 and the first reported use of gene editing technology to modify nonviable human embryos in 2015.