Ask any expectant couple what they hope their baby will be, and one answer is likely to be “healthy.”

But one gene gone awry can imperil a child’s health, causing serious disease or a disability that leaves one more susceptible to health issues. With advances in gene-editing technology, biomedicine is entering an uncharted era in which a genetic mutation can be reversed, not only for one person but also for subsequent generations.

Public debate has swirled around genetic engineering since the first experiments in gene splicing in the 1970s. But the debate has taken on new urgency in recent years as gene modification has been simplified with CRISPR (clustered regularly interspaced short palindromic repeats) technology.

Scientists have compared the technology to word processing software: It acts like a cursor placed next to a typo, capable of editing a gene at a level so granular that it can change a single letter in a long genetic sequence.

While still theoretical in eliminating disabilities, the prospect of erasing some disabilities and perceived deficiencies hovers at the margins of medical ethics. “People are understandably very scared of it, of the many different roads it could take us down as a society,” said Meghan Halley, a bioethics researcher at Stanford University and mother of three children, including a 5-year-old with a disability. “Broadly speaking, this is always going to be problematic because of the many things that disability means.”

CRISPR is widely seen as holding great promise for treating diseases that until now have been intractable.

There are two main types of CRISPR-based editing. One is the correction of a gene in an individual living with a condition or disease. This is known as somatic cell editing (“somatic” refers to the body). In June, NPR reported that Victoria Gray, a woman with sickle cell disease, experienced a significant decrease in her episodes of painful sickle crises in the first year after gene-editing treatment.

In the future, her children or grandchildren may be able to take advantage of the other type of CRISPR “fix”: an edit to the human germ line. This involves making changes to a fertilized egg that not only last through the life of an individual but are passed on to future generations.

This type of “inheritable” gene editing is not applicable to conditions like autism or diabetes, in which the hereditary component is caused by many different genes. But it is suited to disorders caused by variation in a single gene. Sickle cell disease fits into that category, as do cystic fibrosis and Duchenne muscular dystrophy.

Yet bioethicists point out that inheritable-gene editing raises large questions, given the dire consequences of an error, as well as the ethical questions that arise at the prospect of erasing disability from human existence. There is also concern that gene editing for health reasons will be out of reach for many because of its cost.

“There absolutely must be broad public discussions about whether we’re ready to use something that has an unprecedented capability of making changes that have the potential to be passed on to subsequent generations,” said Dana Carroll, a biochemistry professor at the University of Utah who is interim director of the Public Impact Program at the Innovative Genomics Institute at the University of California, Berkeley.

The debate grew more heated in 2018 after a scientist in China announced the birth of the world’s first gene-edited babies — twin girls — using CRISPR to give them immunity to HIV. The announcement generated outrage around the world. In December 2019, a court in China sentenced the scientist to three years in prison for carrying out “illegal medical practices.”

Last year, scientists from seven countries called for a global moratorium on changing inheritable DNA to make genetically modified children.

Less ethically freighted are therapies to cure serious diseases in people who are already living with them. “I think that there are opportunities to use gene-editing technologies to treat genetic diseases that don’t raise the societal implications of altering permanently patterns of human inheritance,” said Dr. Alex Marson, director of the Gladstone-UCSF Institute of Genomic Immunology.

“This is an opportunity for patients to consent to these procedures and be involved in the discussions about the risks and benefits in ways that wouldn’t be possible by intervening in an embryo,” Marson said. “Plus, the modification … wouldn’t affect future generations.”

Yet, according to interviews with parents of children with disabilities, as well as the children themselves, many are ambivalent about gene editing in general.

Ruthie Weiss, 13, was born with oculocutaneous albinism, a genetic disorder impairing her vision that could theoretically be addressed by CRISPR.

“If there was someone who could have waved a magic wand and made the whole thing go away, we would have done that in an instant,” said Dr. Ethan Weiss, Ruthie’s father. Yet now, Weiss said, having watched Ruthie grow up, “We’re blessed to have her as she is.”

That ambivalence toward gene editing was reflected in a 2018 Pew Research Center survey, which found that a majority of Americans approved of gene editing that would result in direct health benefits, while they considered the use of such techniques to bolster a baby’s intelligence to be going “too far.”

The survey also found that the biggest worry was that gene editing would be available only to those who could afford it.

“That’s a critical ethical issue,” Marson said. “We have a real responsibility when we develop these technologies to think about how to make them scalable and accessible.”

Lizzie Nattinger and Fabrizio Pirolo, who live in Brooklyn, N.Y., went through a scare this year when, during Nattinger’s pregnancy with their first child, a routine ultrasound in the second trimester showed a bowel abnormality that might indicate a marker for cystic fibrosis or Down syndrome.

Results of further testing came back showing no such markers, and their son, Giacomo, was born in mid-June. But in the weeks that they were facing uncertainty, the couple fretted over whether they might have to choose between terminating the pregnancy and caring for and raising a severely disabled child.

“I already felt emotionally connected to the baby,” Nattinger said. “It set off a chain of really big questions.”

Knowing that gene editing might be an option should their next child need it leaves Nattinger and Pirolo without a clear answer.

“It’s a really tough, tough choice, looking at it in a vacuum, as an individual, versus looking at it from a bigger societal perspective,” Pirolo said. “I think those are really at odds with each other.”