3.7: Characteristics of Newborns

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 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 3.7 – A newborn being weighed. Image Source: Trei Brundrett is licensed under CC BY-SA 2.0. Wikimedia Commons.

• 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 3.7.1 – Body proportions from infancy to adulthood.

Image Source: Growth and Development. NurseKey. From Patton KT, Thibodeau GA: The human body in health and disease, ed 6, St Louis, 2014, Mosby.)

• 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.

Fontanels, or soft spots:

• soft membranous gaps (soft spots) between the bones on the top of the skull of the newborn
• allow for not only easier delivery but also rapid stretching as the brain develops. These areas of the skull
• will fuse together between the second and eighteenth months to form the harden skull.

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.

Lanugo

• a fine, downy body hair the fetus develops while in the uterus
• protects the fetus and keeps it warm
• common in preterm newborns
• sheds within a few weeks

Figure 3.7.2. Newborn with languo.

Image Source: What is Languo? Health Library Cleveland Clinic.

Scalp Hair

Some infants are born with lush heads of hair, and some may be nearly bald. Other babies may have very fine, almost invisible hair. Amongst fair-skinned parents, this fine hair may be blond, even if the parents are not.

The hair follicles that grow while the fetus develops form a hair pattern they will have for the rest of their lives. Most of the hair a baby is born with is lost in their first 6 months of life. Even little ones born with an entire head of hair can go bald within the first weeks after birth as they are no longer receiving the hormones they get from the mother while in utero. The old hair falls out when the new growth cycle begins and it's normal for the baby to have patchy or bald spots as the new hair comes in. It’s hard to predict what the baby’s new hair will look like. Genes can interact in unexpected ways depending on the baby's family lineage. Parents who both have blonde hair can have babies with dark or red hair,. Likewise a baby born with straight hair may end up with curly hair.

The scalp may also be temporarily bruised or swollen, especially in hairless newborns.

Skin and Body

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 a normal tone.

Figure 3.7.3. Baby on mother's belly immediately after birth, skin covered in vernix and some blood.

Image Source. Postpartum Baby. Wikimedia Commons. Licensed under the Creative Commons Attribution-Share Alike 2.0 Generic

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.

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

A newborn's genitals are enlarged and reddened, with male infants having an unusually large scrotum. The baby's 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.

Newborns will lose many of these physical characteristics quickly.

• Sleep

A newborn typically sleeps approximately 12-16 hours throughout a 24-hour period. At this stage they cannot distinguish between night and day, and their sleep cycles may be as brief as 20-50 minute at one time. They wake because they need to be fed or changed. This pattern alternating short bursts of wake and sleep cycles lasts about three months, when babies begin to recognize the difference between night and day.

Fig 3.7.4. Sleeping baby.

Image Source: brytny.com. Baby Laying on a Blanket. Unsplash.

• Reflexes

Newborns are equipped with several reflexes, which are involuntary movements in response to stimulation

• sucking reflex: when a nipple is inserted into the baby's mouth they should begin sucking
  • the newborn has to figure out how to suck while breathing and swallowing at the same time
• rooting reflex: helps the baby find and latch onto a nipple to feed
• grasping reflex (Palmar grasp): the baby's hand closes around an object when their palm is touched or stroked
• grasping reflex (Plantar grasp or Babinski reflex): when a finger is placed below the baby’s toes, they curl their toes around it
• stepping reflex: when a baby us held in a standing position and their soles touch a surface they will place one foot in front of the other in a "walking" motion

These reflexes disappear within the first 4-6 months. Other reflexes such as eye-blinking, swallowing, sneezing, gagging, and withdrawal reflex are lifelong and serve important function. It is important to monitor reflexes as this can provide insight to the proper development of the brain and it’s connections to the body.

Fig. 3.7.5. Baby sucking on pacifier.

Image Source: Beeki. Baby Sucking on Pacifier. Pixabay.

• Sensory Capacities

Throughout much of history, the newborn was considered a passive, disorganized being who possessed minimal abilities. However, current research techniques have demonstrated just how developed the newborn is with especially organized sensory and perceptual abilities.

Vision

The womb is a dark environment void of visual stimulation. Consequently, vision is the most poorly developed sense at birth and time is needed to build those neural pathways between the eye and the brain. Newborns typically cannot see further than 8 to 16 inches away from their faces, and their visual acuity is about 20/400, which means that an infant can see something at 20 feet that an adult with normal vision could see at 400 feet. Thus, the world probably looks blurry to young infants.

Newborns are able to see light and dark but are not able to discern shapes and patterns, and will slowly develop the capacity to see bright colors. At 2 months, babies' eyes don't yet work well together and it may appear the baby's eyes are crossed or they wander. This is completely normal and will improve as the baby grows and develops. By 3 months, babies can follow a moving object with their eyes and recognize familiar faces.

Hearing

The infant’s sense of hearing is very keen at birth, and the ability to hear is evidenced as soon as the 7th month of prenatal development. In fact, an infant can distinguish between very similar sounds as early as one month after birth and can distinguish between a familiar and unfamiliar voice even earlier. Infants are especially sensitive to the frequencies of sounds in human speech and prefer the exaggeration of infant-directed speech, which will be discussed later. Newborns also prefer their mother’s voices over another female when speaking the same material Additionally, they will register in utero specific information heard from their mother’s voice.

• Early Hearing

Studies show that infants whose mothers had read to them before they were born, later showed a preference for the stories that their mothers read to them while in the womb. In one study the mothers read the first 28 paragraphs of Dr. Seuss's book The Cat in the Hat, beginning when they were 7 months pregnant. The fetuses had been exposed to this story an average 67 times for 3.5 hours. After they were born, tests show the infants were able to "choose" (how fast they sucked on their pacifiers) between recordings of two stories, one of which was The Cat in the Hat, the mothers had read to them while in the womb.

Fig. 3.7.6. Book Cover Dr. Suess. The Cat in the Hat.

Image Source: Book Cover Dr. Suess. The Cat in the Hat.Wikipedia.com

Touch and Pain

Immediately after birth, a newborn is sensitive to touch and temperature, and is also highly sensitive to pain, responding with crying and cardiovascular responses . Newborn boys who are circumcised (the surgical removal of the foreskin of the penis) without anesthesia experience pain as demonstrated by increased blood pressure, increased heart rate, decreased oxygen in the blood, and a surge of stress hormones. Research has demonstrated that infants who were circumcised without anesthesia experienced more pain and fear during routine childhood vaccines. Fortunately, many circumcisions are now done with the use of local anesthetics.

Taste and Smell

Studies of taste and smell demonstrate that babies respond with different facial expressions, suggesting that certain preferences are innate. Newborns can distinguish between sour, bitter, sweet, and salty flavors and show a preference for sweet flavors. Newborns also prefer the smell of their mothers. An infant only 6 days old is significantly more likely to turn toward its own mother’s breast pad than to the breast pad of another baby’s mother Within hours of birth an infant also shows a preference for the face of its own mother.

Infants seem to be born with the ability to perceive the world in an intermodal (stimulation from more than one sensory modality). For example, infants who sucked on a pacifier with a smooth surface preferred looking at visual models of a pacifier with a smooth surface. In contrast, babies given a pacifier with a textured surface preferred to look at a visual model of a pacifier with a textured surface.

Source

• Lally, Martha and Suzanne Valentine-French. Lifespan Development: A Psychological Perspective. (Page 76-77). Licensed under CC BY-NC-SA 3.0