infant infant an infant or baby is the very young offspring of human beings. infant (from the latin word infans, meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term baby. the terms may also be used to refer to juveniles of other organisms. a newborn is, in colloquial use, an infant who is only hours, days, or up to one month old. in medical contexts, a newborn or neonate (from latin, neonatus, newborn) is an infant in the first 28 days after birth; the term applies to premature, full term, and postmature infants. a newborn infant being held by an adult man part of a series onhuman growthand development stages gamete zygote embryo fetus infant toddler child preadolescent adolescent emerging and early adulthood young adult middle adult old adult dying biological milestones fertilization pregnancy childbirth walking language acquisition puberty menopause ageing death development and psychology pre- and perinatal infant and child nature versus nurture adolescent youth young adult adult maturity developmental stage theories attachment ecological psychosocial psychosexual development moral cognitive cultural-historical evolutionary psychology portal before birth, the offspring is called a fetus. the term infant is typically applied to very young children under one year of age; however, definitions may vary and may include children up to two years of age. when a human child learns to walk, they are called a toddler instead. other uses in british english, an infant school is for children aged between four and seven. as a legal term, infancy is more like minority, and continues until a person reaches 18 years of age. physical characteristics 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. head eight-month-old infant; as a common feature, eyes are usually large in relation to the face.a newborn's head is very large in proportion to the body, and the cranium is enormous relative to his or her face. while the adult human skull is about one seventh of the total body length, the newborn's is about 1⁄4. normal head circumference for a full-term infant is 33–36 cm at birth. at birth, many regions of the newborn's skull have not yet been converted to bone, leaving "soft spots" known as fontanels. the two largest are the diamond-shaped anterior fontanel, located at the top front portion of the head, and the smaller triangular-shaped posterior fontanel, which lies at the back of the head. later in the child's life, these bones will fuse together in a natural process. a protein called noggin is responsible for the delay in an infant's skull fusion. 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. hair thin brown hair of a one-year-old infant girl 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 35.6–50.8 cm (14.0–20.0 in), 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 3.4 kg (7+1⁄2 lb), and is typically in the range of 2.7–4.6 kg (6.0–10.1 lb). 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/kg/day. skin a newborn infant, seconds after delivery. amniotic fluid glistens on her skin, and the umbilical cord is still attached. 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 main article: adaptation to extrauterine life 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 one vein. the two arteries carry blood from the baby to the placenta while one vein carries blood back to the baby. genitals a newborn's genitals are enlarged and reddened, with male infants having an unusually large scrotum. the breasts may also be enlarged, even in male infants. this is caused by naturally occurring maternal hormones and is a temporary condition. females (and even males) may actually discharge milk from their nipples (sometimes called witch's milk), or a bloody or milky-like substance from the vagina. in either case, this is considered normal and will disappear with time. care and feeding further information: infant bathing a crying infant in japan in the naki sumo crying baby festival infants cry as a form of basic instinctive communication. a crying infant may be trying to express a variety of feelings including hunger, discomfort, overstimulation, boredom, wanting something, or loneliness. 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. adequate food consumption at an early age is vital for an infant's development. the foundations of optimum health, growth, and neurodevelopment across the lifespan are established in the first 1000 days of life. from birth to six months, infants should consume only breast milk or an unmodified milk substitute. as an infant's diet matures, finger foods may be introduced as well as fruit, vegetables and small amounts of meat. as infants grow, food supplements can be added. many parents choose commercial, ready-made baby foods to supplement breast milk or formula for the child, while others adapt their usual meals for the dietary needs of their child. whole cow's milk can be used at one year, but lower-fat milk is not recommended until the child is 2 to 3 years old. weaning is the process through which breast milk is eliminated from the infant's diet through the introduction of solid foods in exchange for milk. until they are toilet-trained, infants in industrialized countries wear diapers. the transition from diapers to training pants is an important transition in the development of an infant/baby to that of a toddler. children need more sleep than adults—up to 18 hours for newborn babies, with a declining rate as the child ages. until babies learn to walk, they are carried in the arms, held in slings or baby carriers, or transported in baby carriages or strollers. most industrialized countries have laws requiring child safety seats for babies in motor vehicles. common care issues baby colic bassinet/crib cradle cap day care diaper rash infant massage immunization pacifier paternal bond swaddling teething benefits of touch a baby being hugged by a soldier experiments have been done with infants up to four months of age using both positive touch (stroking or cuddling) and negative touch (poking, pinching, or tickling). the infants who received the positive touch cried less often and vocalized and smiled more than the infants who were touched negatively. infants who were the recipients of negative touch have also been linked with emotional and behavioral problems later in life. a lower amount of physical violence in adults has been discovered in cultures with greater levels of positive physical touching. language development an infant holding a space-themed baby book caregivers of an infant are advised to pick up on the infant's facial expressions and mirror them. reproducing and empathizing with their facial expressions enables infants to experience effectiveness and to recognize their own actions more easily (see mirror neurons). exaggeratedly reproduced facial expressions and gestures are recommended, as they are clearer forms of expression. the baby's babbling should also be picked up and repeated. by imitating each other's sounds the first simple dialogues are initiated. accentuated pronunciation and melodic intonation make it easier to recognize individual words in a sentence. however, it is not advisable to use simplified "baby talk" (e.g. "did you 'ouch'?" instead of, "did you hurt yourself?"). even if parents cannot yet understand infants' babbling, a timely response by parents to babbling leads to faster language acquisition. this was confirmed by researchers who first studied mothers' behavior towards 8-month-old infants and later tested the infants' vocabulary when they were 15 months old. a first important development of infants is the discovery that they can influence their parents through babbling (development of intentional communication). parents can encourage this by engaging with their infants in babbling. this in turn promotes further language development, as infants then turn to their parents more often. previous studies have shown that the infant's speech is encouraged when parents, for example, smile in the infant's direction or touch the infant every time the infant looks at them and babbles. it also helps if parents respond to what they think their baby is saying (for example, giving a ball or commenting when the baby looks at the ball and babbles). responding to sounds produced when the baby looks at an object (object-directed vocalizations) thus provide an opportunity to learn the name of the object. in this way, babies also learn that sounds are associated with objects. however, language development is only achieved if parents react positively (e.g. smile) in response to the infant's babbling. a high response rate without a connection to the infant's utterances does not lead to language promotion. it is detrimental to language development if a mother instead tries to divert the infant's attention to something else. sleep main article: infant sleep a sleeping infant a 2018 review analysed 146 studies on infant sleep behavior and listed several factors that show an effect on sleep duration and the number of night wakings. for example, stimulating daytime activities, reading aloud before sleeping, early bedtime, a sleep routine, and avoiding television and media exposure before bedtime are associated with longer sleep duration and fewer nighttime awakenings.: 24 furthermore, strong parental involvement at falling asleep is associated with shorter sleep duration, slower falling asleep and more frequent night-time awakenings in the studies analysed. strong parental involvement is understood to include parental presence, cradling, or breastfeeding at bedtime, as well as carrying the infant to sleep and then putting the infant down. strong parental involvement has a negative effect on infant sleep because the infant cannot develop the ability to self-soothe. on the other hand, low parental involvement