Menstruation is defined as precocious if it starts before the child reaches the age of:

Precocious puberty is the appearance of appropriate secondary sexual characters before the age of 8 years and occurrence of menstruation before 10 years of chronological age. Also know : Delayed puberty : is considered delayed when the secondary sexual characters do not appear by the age of 14, and menarche is not established by 16 years of age.