Belgium said yes. But what does that mean for parents in the United States?

While euthanasia is against the law in most of the world, this week Belgium became the first country to allow terminally ill children to choose to end their lives.

The Belgian law sets up strict parameters under which children would be allowed to ask for euthanasia—from parents’ consent to the supervision of a psychologist. But the ground-breaking move in Europe raises questions for parents in the U.S. too. At what age does a child truly understand death?

“We all tend to think that children don’t have any understanding at all,” says Dr. Adam Naddelman, president of Princeton Nassau Pediatrics in New Jersey. “But kids actually know and understand more than we actually give them credit for.”

In a 2009 study, 90% of adolescent cancer survivors interviewed said that terminally ill children should be free to make end-of-life decisions. The study’s results seemed to show that ill adolescents want to be involved in medical decision-making at the end of life, and that they value a certain degree of autonomous decision-making.

But euthanasia opponents warn of children’s ability to take a leading role in critical decisions like the ones surrounding life-death choices.

In the wake of Belgium’s vote, Sonja Develter, a Belgian nurse who has treated 200 cases of terminally ill children, argued that minors may not have the mental capacity or the vocabulary for requesting to die. “In my experience as a nurse, I never had a child asking to end his life. Children indeed say, ‘It’s really hard’ or I’m fed up,’ but that doesn’t mean they’re tired of living.” she said. “It means they’re tired of their situation.”

Critics of euthanasia in the U.S. echoed her sentiments.

“Kids don’t have the capacity, the judgement to make sound decisions,” said Dr. John Haas, president of The National Catholic Bioethics Center, an organization dedicated to the analysis of moral issues surrounding health care, and one that does not support euthanasia. “Kids might be the ones requesting it, but ultimately, kids won’t be the ones making decisions, it will be made by adults.”

The Belgian government isn’t the first one to consider including children in euthanasia legislation. The Netherlands was the first to legalize euthanasia, in 2002, allowing it in special cases for seriously sick patients 12 years or older. And for some, the recent extension to children is just the normal next step.

“I don’t see it as anything so dramatic,” says Peter Singer, professor of bioethics at the Princeton University Center for Human Values. “The biggest step is to legalize euthanasia in the first place.”

In the U.S., four states—Oregon, Washington, Montana, and Vermont—allow assisted suicide, and others—like Massachusetts and Connecticut—are currently considering legislation.

“The United States might not be ready for the active involvement of physicians,” says Singer. “But the movement to allow lethal doses administered by medical personnel to patients is spreading.”

Belgium’s decision – where 75% of the population supports the measure – is making countries that currently allow euthanasia wonder: why can’t terminally ill minors, working in agreement with their health providers and their family, be allowed to make a decision that they could take on their 18th birthday?