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@angelaretail It was not as common as it is now. Now, most 10 year olds have gotten them. In the 70s and 80s the average was closer to 12. https://t.co/duX9NQxamF for older data
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Age @ Menarche & Time to Establish Regular Menstrual Cycling in Japanese ♀ Born Between 1930 & 1985 http://t.co/ZuthHhpY