"Amenorrhea refers to the absence of menstruation- either one or more missed menstrual periods." Amenorrhea is classified as primary and secondary.
In primary amenorrhea, menstrual periods have never begin (by age 16), while in secondary amenorrhea, there is an absence of menstrual periods for three consecutive cycles or for a time period of more than six months in a person who was previously menstruating.
There are several factors that trigger amenorrhoea, such as:
Pregnancy is the obvious reason for a woman to miss her period. However, pregnancy, menopause and breastfeeding do not cause amenorrhea.
Contact your doctor if you've missed at least three menstrual periods in a row or if your daughter has never had a menstrual period and is 16 years or older.