Queen Paola, 85, has had a fall and needs rest, the Royal Palace said on Monday, adding that she was expected to recover quickly.
The Queen will therefore not be present at the opening ceremony of the 2022-2023 academic year at the Royal Military School (ERM), which her grandson, Prince Gabriel, will now enter.
Her husband, King Albert II, will be present at the ceremony, as well as King Philippe, Queen Mathilde and two of their children, Prince Emmanuel and Princess Eléonore.
The Queen had already had a fall in March, when she then broke her humeral neck and had to rest for eight weeks.
Queen Paola was queen of Belgium during the reign of King Albert II, from 9 August 1993 to 21 July 2013.
