Last week, as STAT reports, a team of scientists at University College London successfully used gene therapy on mice fetuses in utero to correct a severe form of Goucher’s disease — a condition in which the body cannot effectively break down fat.

Gene therapy is still relatively theoretical, and it is not without controversy in the scientific world. The process involves attaching a corrective gene to a virus, which is then sent into a patient’s cells. As STAT points out, this gene-virus rig could potentially be sent into a pregnant woman’s womb to remedy a disease before the fetus is born. Experts say this preventative method has biological advantages to treating the disease after birth.

In the study conducted last week, affected mice treated in utero were born no different to their littermates, who didn’t have Goucher’s disease. Mice who were treated soon after they were born showed some positive improvement, but not to the same extent as those treated before birth. Simon Waddington, one of the UCL scientists who conducted the study, said they studied Gaucher’s disease because of how harmful it is: Human babies born with it suffer from brain and organ damage, and usually die within a few years.

But gene therapy is not without problems, and we don’t know the full extent of its potential repercussions. Some scientists point out that gene therapy of this kind could trigger an immune response in the fetus, which would affect the corrective gene attached to the virus. It’s also possible that the mother could take on some of the corrective genes intended for the fetus, and scientists have no substantial idea of what effect this could have on the pregnant woman; in 1999, a patient died in a clinical gene therapy trial.

Additionally, gene therapy is an ethical grey area. As STAT notes, there are moral and financial implications to giving a person life, when they would otherwise have died at 2, if, for example, the treatment only allowed them to live to the age of 25 and with severe disabilities.

Many scientists still believe gene therapy is promising, however. “As the entire field of gene therapy, both prenatal and postnatal, has advanced over the last 10 to 15 years, there has been an acknowledgement that it is a true possibility for the future,” Dr. William Peranteau, a pediatric and fetal surgeon who co-authored a recent review of gene therapy, told STAT.

If developed, experts believe gene therapy would only be used for a limited number of cases, for a limited number of diseases — those that start inflicting serious, irreparable damage to the fetus during pregnancy. Scientists would first have to fully understand the genetic mechanisms behind the disease. Timing is also key: Doctors would need to be able to identify the disease early enough in the pregnancy, before it caused irreversible harm.

There are several steps to go before gene therapy can be safely used on humans (as STAT notes, the 1999 incident is a warning against rushing into clinical trials too quickly), not to mention the ethical questions to be weighed. But a more hopeful reading of last week’s mouse study is the potential that, as gene therapy develops in sophistication, so, too, will regenerative science; consequently, individuals who are saved by gene therapy in future might be able to lead regular lives.