First period

Menarche is not the start of puberty

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Plain language, with the medical term given alongside.

Puberty runs in a sequence, and bleeding is near the end of it. Breast budding — thelarche — is the usual first visible sign, and the first period typically follows two to three years later. Growth in height peaks before menarche, not after, which is why the growth spurt is largely finished by the time periods begin.

Step 1

Thelarche

Breast budding. The first visible sign of puberty, and the point from which the clock to menarche is counted.

Step 2

Pubarche

Pubic hair, driven by adrenal androgens. Can precede or follow thelarche.

Step 3

Growth peak

Peak height velocity, typically before menarche. Most remaining growth happens before the first period.

Step 4

Menarche

The first period. Usually two to three years after thelarche, and 98% have started by 15.

Why this matters practically: if breast development started three years ago and no period has arrived, that is a specific finding worth raising, and it is measured from the breast changes rather than from a birthday. It also means a girl who has not started her period is not necessarily "behind" — she may simply have started puberty later.The thelarche-to-menarche interval is the operative measure. Primary amenorrhea is defined as no menarche by 15 in the presence of secondary sexual characteristics, or more than 3 years post-thelarche, or absent thelarche by 13 — the last of which shifts the differential toward gonadal failure and hypogonadotropic causes rather than outflow obstruction.