An infant (from the Latin word infans, meaning "unable to speak" or "speechless") is the more formal or specialised synonym for "baby", the very young offspring of a human. The term may also be used to refer to juveniles of other organisms.
A newborn's shoulders and hips are wide, the abdomen protrudes slightly, and the arms and legs are relatively long with respect to the rest of their body. The Apgar score is a measure of a newborn's transition from the uterus during the first minutes after birth.
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.
During labour and birth, the infant's skull changes shape to fit through the birth canal, sometimes causing the child to be born with a misshapen or elongated head. It will usually return to normal on its own within a few days or weeks. Special exercises sometimes advised by physicians may assist the process.
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.
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. Occasionally, hospitals may apply triple dye to the umbilical stub to prevent infection, which may temporarily color the stub and surrounding skin purple.
Breastfeeding is the recommended method of feeding by all major infant health organizations. If breastfeeding is not possible or desired, bottle feeding is done with expressed breast-milk or with infant formula. Infants are born with a sucking reflex allowing them to extract the milk from the nipples of the breasts or the nipple of the baby bottle, as well as an instinctive behavior known as rooting with which they seek out the nipple. Sometimes a wet nurse is hired to feed the infant, although this is rare, especially in developed countries.
Infants respond to the sound of snake hissing, angry voices of adults, the crackling sound of a fire, thunder, and the cries of other infants. They have a drop in heart rate, their eyes blinking, increased turning toward the speakers or parent, all of these indicating that they were paying more attention. This is believed by some to be evolutionary response to danger. Babies' ability to accurately locate sounds is refined during their first year.
There is a positive relationship between national wealth and good health. The rich and industrialized countries of the world, prominently Canada, the United Kingdom, the United States, and Japan, spend a large proportion of their wealthy budget on the health care system. As, a result, their health care systems are very sophisticated, with many physicians, nurses, and other health care experts servicing the population. Thus, infant mortality is low. On the other hand, a country such as Mexico, which spends disproportionately less of its budget on healthcare, suffers from high mortality rates. This is because the general population is likely to be less healthy. In the U.S., infant mortality rates are especially high in minority groups. For instance, non-Hispanic black women have an infant mortality rate of 13.63 per 1000 live births whereas in non-Hispanic white women it was much lower at a rate of 5.76 per 1000 live births. The average infant mortality rate in the U.S. is 6.8 per 1000 live births.