Amenorrhea is the absence of menstruation — one or more missed menstrual periods. Women who have missed at least three menstrual periods in a row have amenorrhea. It may be primary or secondary.
- Primary amenorrhea is the absence of menstrual bleeding and secondary sexual characteristics (for example, breast development and pubic hair) in a girl by age 14 years or the absence of menstrual bleeding with normal development of secondary sexual characteristics in a girl by age 16 years.
- Secondary amenorrhea is the absence of menstrual bleeding in a woman who had been menstruating but later stops menstruating for three or more months in the absence of pregnancy, lactation (the ability to breastfeed), cycle suppression with systemic hormonal contraceptive(birth control) pills, or menopause.
