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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Primary amenorrhea is absence of menstruation by the age of
assistant
The correct answer is  Primary amenorrhea refers to the failure of the onset of menstruation beyond the age of 16 years regardless of the development of secondary sexual characters Ref: Shaw Gynecology 17 e pg 141.