What is the average age of menarche, and by what age would absence be considered primary amenorrhea?

• A. Average age 12; absent by 16
• B. Average age 12.5; absent by 16
• C. Average age 13; absent by 15
• D. Average age 11.5; absent by 14

Answer: (B)

Menarche timing shows most girls begin in the early teens, with the average around 12.5 years. If a girl has not begun menstruating by age 16, this is considered primary amenorrhea, provided her secondary sexual development has progressed normally. Some guidelines note 13 as a cutoff if there is absent or delayed secondary sexual characteristics, but the common exam standard uses 16 for the threshold when development has been normal. That’s why the option with an average of 12.5 and a 16-year cutoff is the best choice.