process. Hair Some newborns have a fine, downy body hair called lanugo. It may be particularly noticeable on the back, shoulders, forehead, ears and face of premature infants. Lanugo disappears within a few weeks. Infants may be born with full heads of hair; others, particularly caucasian infants, may have very fine hair or may even be bald. Amongst fair-skinned parents, this fine hair may be blonde, even if the parents are not. An infant's hair color and texture can change: red can give way to blond, curly can go straight, and thick, dark hair could reappear a lot sparser and lighter. The scalp may also be temporarily bruised or swollen, especially in hairless newborns, and the area around the eyes may be puffy. Length In developed countries, the average total body length of a newborn is , although premature newborns may be much smaller. The way to measure a baby's length is to lay the baby down and stretch a measuring tape from the top of the head to the bottom of the heel. Weight In developed countries, the average birth weight of a full-term newborn is approximately , and is typically in the range of . Over the first 5–7 days following birth, the body weight of a term neonate decreases by 3–7%, and is largely a result of the resorption and urination of the fluid that initially fills the lungs, in addition to a delay of often a few days before breastfeeding becomes effective. After the first week, healthy term neonates should gain 10–20 grams/day. Skin Immediately after birth, a newborn's skin is often grayish to dusky blue in color. As soon as the newborn begins to breathe, usually within a minute or two, the skin's color reaches its normal tone. Newborns are wet, covered in streaks of blood, and coated with a white substance known as vernix caseosa, which is hypothesised to act as an antibacterial barrier. The newborn may also have Mongolian spots, various other birthmarks, or peeling skin, particularly on the wrists, hands, ankles, and feet. Umbilical cord The umbilical cord of a newborn is bluish-white in color. After birth, the umbilical cord is normally cut, leaving a 1–2 inch stub. The umbilical stub will dry out, shrivel, darken, and spontaneously fall off within about 3 weeks. This will later become a belly-button after it heals. The umbilical cord contains three vessels: two arteries and