6.4: Newborn Characteristics

Size

The average newborn in the United States weighs about 7.5 pounds and is about 20 inches in length. For the first few days of life, infants typically lose about 5 percent of their body weight as they eliminate waste and get used to feeding. This often goes unnoticed by most parents, but can be cause for concern for those who have a smaller infant. This weight loss is temporary, however, and is followed by a rapid period of growth.

Figure \(\PageIndex{1}\): A newborn is weighed as soon as they are born and then multiple times after birth and at their well baby visits.[1]

Body Proportions

The head initially makes up about 50 percent of our entire length when we are developing in the womb. At birth, the head makes up about 25 percent of our length (think about how much of your length would be head if the proportions were still the same!).

Figure \(\PageIndex{2}\): Body proportions from infancy to adulthood – this graph shows how body dimensions change not only in size but proportionality with age.[2]

Brain Development

Some of the most dramatic physical change that occurs during this period is in the brain. At birth, the brain is about 25 percent its adult weight and this is not true for any other part of the body. While most of the brain’s 100 billion neurons are present at birth, they are not fully mature. During the next several years dendrites or connections between neurons will undergo a period of transient exuberance or temporary dramatic growth.[3]

Appearance at Birth

During labor 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.

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. Likewise, not all infants are born with lush heads of hair. Some may be nearly bald while others may have very fine, almost invisible hair. Some babies are even born with a full head of hair. Amongst fair-skinned parents, this fine hair may be blond, even if the parents are not. The picture shows lanugo on the shoulders of newborn twins.

Figure \(\PageIndex{3}\): Lanugo on the shoulder and back of twin girls.[4]

Figure \(\PageIndex{4}\): A newborn baby covered in vernix.[5]

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 returns to its normal tone. Newborns are wet, covered in streaks of blood, and coated with a white substance known as vernix, which is thought to act as an antibacterial barrier, seen in the figure.

The scalp may be temporarily bruised or swollen, especially in hairless newborns, and the area around the eyes may be puffy.

The newborn may also have slate grey nevi (blue or blue black birthmark on the lower back that used to be called Mongolian blue spots), various other birthmarks, or peeling skin, particularly on the wrists, hands, ankles, and feet. [6]

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.

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. Occasionally, hospitals may apply triple dye to the umbilical stub to prevent infection, which may temporarily color the stub and surrounding skin purple.

Figure \(\PageIndex{5}\): The clamping and cutting of a newborn’s umbilical cord is one of the first things that is done once the baby is born.[7]

Newborns lose many of the above physical characteristics quickly. Thus, older babies look very different. While older babies are considered "cute," newborns can be "unattractive" by the same criteria and first time parents may need to be educated in this regard.[8] A funny story that used to be told in my own family is that when my own mother’s friends and family came to visit her in the hospital after my birth, they remarked in private on what an ugly little newborn I was! My baby pictures don’t bear out that initial disappointment though (at least I hope not :)). **maybe put baby photo of self here**

Sleep

Figure \(\PageIndex{6}\): An older infant sleeps often in the day[10]

Attributions:

Child Growth and Development by Jennifer Paris, Antoinette Ricardo, and Dawn Rymond, 2019, is licensed under CC BY 4.0

[1] Image by Trei Brundrett is licensed under CC BY-SA 2.0

[2] Image is in the public domain

[3] Lifespan Development - Chapter 4: Infancy - Physical Development by Lumen Learning references Psyc 200 Lifespan Psychology by Laura Overstreet, licensed under CC BY 4.0

[4] Image is in the public domain

[5] Image by Upsilon Andromedae is licensed under CC BY 2.0

[6] Mongolian Spot by Wiktionary is licensed under CC BY-SA 3.0

[7] Image by NNethala is licensed under CC BY-SA 3.0

[8] Infant by WikiDoc is licensed under CC BY-SA 3.0

[9] Lifespan Development: A Psychological Perspective (page 71) by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0

[10] Image by brytny.com on Unsplash