In case either the mother of the emperor was already dead or the rank of the real mother was too low, 'Junbo' (a woman who was given the status equivalent to the emperor's birth mother) was assigned to be the mother.
天皇の母がすでに死去している場合、または生母の身分が低すぎる場合などに、母に擬して准母を定めることが行われた。