Menarche is a girl’s first menstrual period, marking the start of menstrual cycles.
What menarche is
Menarche is a girl’s first menstrual period, usually occurring around age 9 to 15. It marks the start of menstrual cycles and is one of the milestones of puberty. After menarche, the body is still developing the hormonal system that controls the menstrual cycle. For that reason, cycles in these early years are often not yet settled and can vary from month to month. The gap between periods can also differ a lot, and this is usually part of normal development.
Why it matters in PCOS
In the first few years after menarche, irregular cycles are common because the hormonal system is still maturing. This means irregularity at this stage does not necessarily point to PCOS. That is why diagnosing PCOS in teenagers calls for caution, so that normal changes are not mistaken for something unusual. A doctor will consider how long it has been since menarche before concluding that irregular cycles need closer attention. You can read more about the signs on the PCOS symptoms page.
How assessment in teenagers differs
Clinical guidelines advise interpreting adolescent PCOS assessment in an age-appropriate way and relative to how long it has been since menarche. Some criteria used for adults, such as the appearance of the ovaries on ultrasound, may not apply directly to teenagers because of the natural changes at this stage. This careful approach helps avoid an overly early or mistaken diagnosis, and the unnecessary worry that can come with it. A doctor may choose to monitor the situation over time before drawing any conclusion. For the basics about the condition, see also what is PCOS.
What it means for you
If your daughter, or you, has irregular periods soon after menarche, this is often part of a normal maturing process. However, if irregularity persists for several years after menarche, or comes with other symptoms such as severe acne or excess hair growth, that is worth discussing with a doctor. Noting the dates of periods can help give the doctor a clearer picture. A doctor or pharmacist can help judge whether further checks are appropriate for your situation.
This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.