Menarche is the term used to describe the first menstrual period in a female adolescent. It is a defining part of the bodys transition from childhood to adulthood, called puberty. Menarche typically occurs between the ages of 10 and 16, with the average age of onset being 12.4 years. However, girls experience menarche at different ages, and the worldwide average age of menarche is difficult to estimate accurately, varying significantly by geographical region, race, ethnicity, and other characteristics.

Menarche is an important milestone during puberty, and it signals the beginning of reproductive abilities. It is closely associated with the ongoing development of secondary sexual characteristics. Before menarche, girls may notice changes in their body such as breast development, widening hips, a growth spurt, oily skin and acne, hair growth on their underarms, and pubic hair growth.

The first menstrual cycles are usually anovulatory with varied lengths and flow. Menarche tends to be painless and occurs without warning. Most females recognize menarche as their bodys critical declaration of fertility.

Menarche is an important time to develop a relationship with a gynecologist. They can answer questions about the changes experienced during puberty, such as how much bleeding is considered "normal" during menarche, when periods should become more predictable, what symptoms can be managed at home, and what symptoms require a doctors visit.