Researchers from Harvard found that girls who are now aged 19 to 24 got their first period when they were 11, on average, compared to women now aged 55 to 74, who were an average age of 12.Researchers from Harvard found that girls who are now aged 19 to 24 got their first period when they were 11, on average, compared to women now aged 55 to 74, who were an average age of 12.Read MoreHealth News | Mail Online