Currently, the law applies to those over 18 but one expert told the upper house of parliament that it was clear that euthanasia was being carried out on younger people, the Belga news agency reported.
"We all know it," said Dominique Biarent, head of intensive care at Queen Fabiola Children's University Hospital in Brussels.
Faced with this reality, "doctors need a legal framework," Biarent was quoted as saying by Belga.
The changes to the law, which would also include sufferers of Alzheimer's disease, were submitted to parliament in December and it is likely to be several months before any decision is taken on them.
Belgium was the second country in the world after the Netherlands to legalise euthanasia in 2002.
A total of 1,133 instances -- mostly for terminal cancer -- were recorded in 2011, about one per cent of all deaths in the country, according to official figures.