Editing Infant (section)

==Physical characteristics==
{{More citations needed|section|date=March 2022}}
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===
[[File:Baby Face.JPG|thumb|Eight-month-old infant; as a common feature, eyes are usually large in relation to the face.|left]]A newborn's head is very large in proportion to the body, and the [[Skull#Humans|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 {{frac|1|4}}. Normal head circumference for a full-term infant is 33–36&nbsp;cm at birth.<ref>{{cite book |author1=Wallace, Donna K. |author2=Cartwright, Cathy C. |title=Nursing Care of the Pediatric Neurosurgery Patient |publisher=Springer |location=Berlin |year=2007 |isbn=978-3-540-29703-1 |url=https://books.google.com/books?id=G6o3uSlfRKcC&pg=PA40 |page =40}}</ref> At birth, many regions of the newborn's skull have not yet been converted to bone, leaving "soft spots" known as [[fontanel]]s. 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 (protein)|noggin]] is responsible for the delay in an infant's skull fusion.<ref>{{cite journal |vauthors=Warren SM, Brunet LJ, Harland RM, Economides AN, Longaker MT | title = The BMP antagonist noggin regulates cranial suture fusion | journal = Nature | volume = 422 | issue = 6932 | pages = 625–9 | date = 2003-04-10 | pmid = 12687003 | doi = 10.1038/nature01545 | bibcode = 2003Natur.422..625W | s2cid = 4331659  | issn=0028-0836 }}</ref>

During [[childbirth|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 [[physician]]s may assist the process.

===Hair===
[[File:Baby hairy head DSCN2483.jpg|thumb|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 [[White people|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.{{Citation needed|date=March 2022}} The [[scalp]] may also be temporarily [[bruise]]d 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 {{convert|35.6|–|50.8|cm|in|abbr=on}}, 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 {{convert|3.4|kg|lb|frac=2|abbr=on}}, and is typically in the range of {{convert|2.7|–|4.6|kg|lb|abbr=on}}.

Over the first 5–7 days following birth, the body weight of a term neonate decreases by 3–7%,<ref name="Mohamed2012">{{EMedicine|article|938854|Neonatology Considerations for the Pediatric Surgeon}}</ref>{{fv|date=November 2024}} 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.<ref name="Mohamed2012" />{{fv|date=November 2024}}

===Skin===
[[File:HumanNewborn.JPG|thumb|A newborn infant, seconds after [[Childbirth|delivery]]. [[Amniotic fluid]] glistens on her skin, and the [[umbilical cord]] is still attached.|left]]
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 spot]]s, various other [[birthmark]]s, or peeling skin, particularly on the wrists, hands, ankles, and feet.

===Umbilical cord===
{{Main|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&nbsp;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.