Decades earlier, in 653, a minor female agrarian rebel leader, Chen Shuozhen (陳碩真), had claimed the title of "Empress Regnant Wenjia" (文佳皇帝), during her rebellion. However, because her rebellion was very limited in scope and was quickly crushed, she is not typically regarded as a true "empress regnant." See Zizhi Tongjian, vol. 199. Earlier than that, during Northern Wei dynasty, Empress Dowager Hu, after her son Emperor Xiaoming's death, falsely declared Emperor Xiaoming's daughter to be a son and declared the daughter to be the new emperor, but almost immediately revealed that the child was in fact female, and thereafter declared Yuan Zhao, the young son of Emperor Xiaoming's cousin Yuan Baohui (元寶暉) emperor. See Zizhi Tongjian, vol. 152. Emperor Xiaoming's daughter is also therefore not usually considered a true emperor.
