Muscle tone
(The five areas that are assessed when the Apgar score is calculated are heart rate, respiratory effort, muscle tone, reflex irritability, and color. The rate of respirations, not the depth, is assessed for an Apgar score. Amount of mucus, degree of head lag, and depth of respirations are not tested for an Apgar score.)
Skin: thin, veins visible; breasts: flat areolae, no buds; plantar creases: absent; lanugo: abundant
The characteristics of preterm, term, and postterm gestational age are based on assessments of physical maturity such as the Ballard or Dubowitz assessment. A preterm infant's skin is translucent, with many visible veins. A term infant has some cracking of the skin and some visible veins, depending on gestational age. Term is any gestation after 38 weeks; veins are less visible at 40 weeks' gestation. The postterm infant typically has dry, leathery, parchmentlike skin with numerous deep wrinkles. The areolae of a preterm infant are flat, without buds, and they become more raised during development, averaging 3 to 4 mm at term and 5 to 10 mm in the postterm infant. The plantar creases develop on the foot during gestation, beginning smooth, then covering two thirds at term, and finally covering the entire sole after term. Lanugo is the fine downy hair that diminishes as the infant develops gestationally.