What is Tanner stage 1 development in children?

The Tanner stages (also known as the Tanner scale) are stages of physical development in children, adolescents and adults. The stages define physical measurements of development based on external primary and secondary sex characteristics, such as the size of the breasts, genitalia, and development of pubic hair.

Due to natural variation, individuals pass through the Tanner stages at different rates, depending in particular on the timing of puberty.

In HIV treatment, Tanner staging is used to determine which treatment regimen to follow (adult, adolescent, or pediatric).

Pubic hair (both male and female)

Tanner I -- no pubic hair at all [10 and under] (prepubertal state)
Tanner II -- small amount of long, downy hair with slight pigmentation at the base of the penis and scrotum (males) or on the labia majora [10-11](female)
Tanner III -- hair becomes more coarse and curly, and begins to extend laterally [12-14]
Tanner IV -- adult-like hair quality, extending across pubis but sparing medial thighs [13-15]
Tanner V -- hair extends to medial surface of the thighs [16+]

Genitals (male)

Tanner I -- prepubertal (testicular volume less than 1.5 ml; small penis of 3 cm or less)
Tanner II -- testicular volume between 1.6 and 6 ml; skin on scrotum thins, reddens and enlarges; penis length unchanged
Tanner III -- testicular volume between 6 and 12 ml; scrotum enlarges further; penis begins to lengthen to about 6 cm
Tanner IV -- testicular volume between 12 and 20 ml; scrotum enlarges further and darkens; penis increases in length to 10cm and circumference
Tanner V -- testicular volume greater than 20 ml; adult scrotum and penis of 15 cm in length

Breasts (female)

Tanner I -- no glandular tissue; areola follows the skin contours of the chest (prepubertal)
Tanner II -- breast bud forms, with small area of surrounding glandular tissue; areola begins to widen
Tanner III -- breast begins to become more elevated, and extends beyond the borders of the areola, which continues to widen but remains in contour with surrounding breast
Tanner IV -- increased breast size and elevation; areola and papilla form a secondary mound projecting from the contour of the surrounding breast
Tanner V -- breast reaches final adult size; areola returns to contour of the surrounding breast, with a projecting central papilla.