9.3: The Newborn

Learning Objectives

1. Describe the typical physical characteristics of newborns.
2. Identify and explain the purpose of newborn assessments.
3. Summarize variations in newborn appearance.

Figure \(\PageIndex{1}\): A new mother holding her newborn. Image by the U.S. Air Force is in the public domain

Characteristics of Newborns

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% of their body weight as they eliminate waste and adjust to feeding. This often goes unnoticed by most parents, but can be a 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 \(\PageIndex{2}\): A newborn being weighed. Image by Trei Brundrett is licensed under CC BY-SA 2.0

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 \(\PageIndex{3}\): Body proportions from infancy to adulthood. Image is in the public domain.

Brain Development

Some of the most dramatic physical change that occurs during this period are in the brain. At birth, the brain is approximately 25 percent of its adult weight, a characteristic unique to the brain among all other parts of the body. While most of the brain’s 100 to 200 billion neurons are present at birth, they are not fully mature. Over the next several years, dendrites, or the connections between neurons, will undergo a period of transient exuberance, characterized by temporary, dramatic growth. ³¹

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 typically returns 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. Among fair-skinned parents, this fine hair may be blond, even if the parents are not. The picture on the left shows lanugo on the shoulders of newborn twins.

Figure \(\PageIndex{4}\): Lanugo on the shoulder and back of twin girls. Image is in the public domain.

Figure \(\PageIndex{5}\): A newborn baby covered in vernix. Image by Upsilon Andromedae is licensed under CC BY 2.0.

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, as seen in the picture to the right.

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

The newborn may also have Mongolian spots (blue or blue black birthmarks on the lower back), various other birthmarks, or peeling skin, particularly on the wrists, hands, ankles, and feet. ³⁴

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 condition is caused by naturally occurring maternal hormones and is typically a temporary issue.

The umbilical cord of a newborn is bluish-white in color. After birth, the umbilical cord is usually cut, leaving a 1–2 inch stub. The umbilical stub will dry out, shrivel, darken, and fall off spontaneously within approximately 3 weeks. Occasionally, hospitals may apply triple dye to the umbilical stump to prevent infection, which may temporarily color the stump and surrounding skin purple.

Figure \(\PageIndex{6}\): The clamping and cutting of a newborn’s umbilical cord. Image by NNethala is licensed under CC BY-SA 3.0.

Newborns lose many of the above physical characteristics quickly. Thus, older babies look very different. While older babies are often considered "cute," newborns can be perceived as "unattractive" by the same criteria, and first-time parents may need to be educated on this aspect. ³⁶

Assessing the Newborn

The Apgar assessment is conducted one minute and five minutes after birth. This is a very quick way to assess the newborn's overall condition. Five measures are assessed: heart rate, respiration, muscle tone (assessed by gently touching the baby's palm), reflex response (the Babinski reflex is tested), and skin color. A score of 0 to 2 is given on each feature examined. An Apgar score of 5 or less is cause for concern. The second Apgar score should indicate improvement with a higher score. ²²

Figure \(\PageIndex{7}\): The Apgar assessment. Image by Event Medicine Group is licensed CC BY 4.0.

Another way to assess the condition of the newborn is the Neonatal Behavioral Assessment Scale (NBAS). The baby's motor development, muscle tone, and stress response are assessed. This tool has been used worldwide to further assess newborns, especially those with low Apgar scores, and to make comparisons between infants in different cultures (Brazelton & Nugent, 1995).

Newborns are also routinely screened for different conditions. Within the first 24 to 48 hours after birth, babies born in hospitals undergo a simple heel stick, and a few drops of blood are collected on a special paper card. Providers test those dried blood spots for a variety of congenital disorders, or conditions that are present at birth. In California, newborns are now screened for 80 different genetic and congenital disorders.

Figure \(\PageIndex{8}\): A medical professional performing the heel stick test. Image by the U.S. Air Force is in the public domain.

Newborns are also screened for hearing disorders and certain serious heart problems using methods other than dried blood spots. ^₂₅

References, Contributors and Attributions

22. Lifespan Development: A Psychological Perspective (page 63) by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0

25. Newborn Screening is in the public domain ; Newborn Screening Program (NBS) by the California Department of Public Health is in the public domain

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

34. Mongolian Spot by Wiktionary is licensed under CC BY-SA 3.0

36. Infant by WikiDoc is licensed under CC BY-SA 3.0

Brazelton, T. B., & Nugent, J. K. (1995). Neonatal Behavioral Assessment Scale (3rd ed.). Cambridge University Press.