Very young offspring of humans
In common terminology, a baby is the very young offspring of human beings, while infant (from the Latin word "infans", meaning 'baby' or 'child') is a formal or specialised synonym. The terms may also be used to refer to juveniles of other organisms. A newborn is, in colloquial use, a baby who is only hours, days, or weeks old; while 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).
Infants born prior to 37 weeks of gestation are called "premature", those born between 39 and 40 weeks are "full term", those born through 41 weeks are "late term", and anything beyond 42 weeks is considered "post term".
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.
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 ;templatestyles src="Fraction/styles.css" / ;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.
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/kg/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 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.
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.
Infants are altricial and are fully dependent on their mothers or an adult caretaker for an extended period of time. 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 1,000 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 two to three 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 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.
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Benefits of touch.
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.
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.
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 awakenings. However, research has indicated that frequent wakings are protective of SIDS.
Infant sleep is not linear, ebbing and flowing with developmental milestones and age.
The National Sleep Foundation gives a rough recommendation on sleep hours, that commonly decreases with increasing age.
Maternal sensitivity.
Maternal sensitivity plays a particular role in the relationship with the infant and for favorable emotional development. This means being attentive to the infant's behavioral expressions, not misinterpreting the infant's expressions because of one's own moods, reacting immediately to the situation and finding a response that is appropriate to the context and the expressed needs. A secure attachment is promoted through empathetic and adequate as well as prompt responses. In accordance with their basic needs, infants show an inborn behavior of seeking closeness to the mother – or to another primary caregiver – and thus in turn foster an attachment. When separated from the mother, infants protest by crying and by body movements.
Other.
Wearing has a calming effect on infants. A 2013 study showed that infants placed in a cradle cried and kicked more often and had an increased heart rate (so the infants were stressed), while those picked up and carried by the mother while walking around calmed down significantly. The effect of being held motionless in the arm was intermediate between that of being carried around and that of being put down. That carrying (e.g., in a baby sling) makes infants more content and makes them cry less had already been shown in a randomized study in 1986.
For infant feeding, breastfeeding is recommended by all major infant health organizations.
Many airlines refuse boarding for all babies aged under 7 days (for domestic flights) or 14 days for international flights. Asiana Airlines allows babies to