What is average age for menarche?

12 and 1/2. For african americans about age 12 and a few months. For whites about 12 and a half. There have been at least five different studies since 2000 which gave slightly different results.
Historically 12.5. But with the obesity epidemic it has moved up a couple years as has secondary sexual devleopment. The reason being - usually the body has to have a certain percentage body fat to begin menarche, thus athletic girls tend to have delayed menarche. A 2011 study found that each 1 kg/m2 increase body-mass index (bmi) can be expected to result in a 6.5% higher absolute risk of early menarche.

Related Questions

What is average age now for menarche?

Dropping. The age at which a girl has the first period depend in several factors. Proper thyroid function and a certain ratio of body fat are necessary. With the increase in calories in modern society, this age is ever younger. In the U.S. , for african american girls closer to 8.5 years old . For other ethnic groups it's closer to 9. Read more...