Growth and development - Infant: Nursing

Infancy is the period of life between birth and the age of 12 months. In this short period of time, infants undergo a series of rapid and dramatic changes involving both their physical growth and the development of motor, cognitive, and social skills that will set the basis for future development. Now, developmental psychologists who were involved in studying infant development include Jean Piaget and Erik Erikson.

Alright, now it’s important to note that growth and development are two different concepts. Growth refers to physical changes in height, weight, and the appearance of the body; whereas development refers to the acquisition of complex motor, cognitive, and social skills, such as walking, speaking, turning a page in a book, or smiling at familiar faces.

Alright, now, let’s start by looking at the first month after birth, during which the infant is called a newborn. Newborns have a distinctive appearance, with a very large head and relatively short arms and legs in relationship to their body. Many newborns still have lanugo, or very thin, soft hair, on some areas of their body, but this usually disappears within a few weeks after birth. Head hair can vary from almost no hair to a full head of hair. Generally, the stub of the umbilical cord remains for a few weeks until it eventually dries up and falls off, giving rise to the navel or umbilicus.

Now, in order to assess an infant's growth, we can look at four parameters: length, weight, head circumference, and the time of closure of the skull’s fontanelles. Starting with length, most infants measure between 45.7 and 60 cm at the time of birth. From there, length is expected to increase by 2.5 cm every month during the first six months, and then slow down until an infant has doubled their height at birth, which is usually around 12 months of age.

In terms of weight, the average birth weight is around 3.5 kg, but this can also vary between 2.5 kg and 4.5 kg for term infants. In the first week after birth, infants can lose between 5 to 10% of their birth weight and then regain it within the first couple weeks. After that, weight typically doubles by 6 months, and it usually triples by the 12 month mark.

Next, there is head circumference, which measures an average of 35 cm at birth, and is typically 3 cm larger than the chest circumference. By the first year of age, head circumference increases roughly by 10 cm and grows proportionally with the chest circumference.

Finally, remember that the fontanelles are the soft spots on the baby’s head. There’s six of them, and the two biggest ones are the anterior fontanelle and posterior fontanelle. At birth, the anterior fontanelle typically measures around 2.1 cm, but this can vary from 0.6 to 3.6 cm; while the posterior fontanelle is typically less than 1 cm. The posterior fontanelle closes by 2 months of age; while the anterior fontanelle closes between 9 and 18 months of age.

Alright, let’s switch gears and look at infant development. Typically, this is discussed in terms of developmental milestones that infants achieve at certain ages. By looking at these milestones, we can see how the infant is developing and keep an eye out for any potential problems. There are four types of milestones that should be assessed: motor,cognitive, social, and psychosocial; and these are typically checked periodically throughout infancy and childhood.

Now, for motor milestones, gross motor skills develop in a cephalocaudal, or head to toe fashion; whereas fine motor skills develop in a proximodistal fashion.

So, at 2 months of age, an infant should be able to keep their head steady when held and also bring their head up and look forward while on their stomach. At 4 months old, infants are able to sit with support, grasp objects with their hands, and start to roll over to one side. At 6 months old, infants should be able to roll both ways and sit upright unsupported for short moments, as well as transfer items from one hand to another.

At 8 to 9 months, infants can sit unsupported, crawl, and hold objects between the pads of the thumb and the index finger. Finally, at the 12 month mark, infants can throw objects and they might be able to stand by themselves and walk with their hands held by another person.

Moving on to cognitive milestones, Piaget explains that infants are in the sensorimotor stage, where they learn about themselves and the world around them by using their senses and manipulating objects.

By 2 months of age, an infant can turn their head when someone is speaking, and can coo, which is a noise that resembles speech. They can also start showing a preference for their usual caregiver over a stranger, paying attention to new things or sounds, and looking at objects until they reach their midline. At 4 months, they might start laughing, squealing, and saying ‘ga.’ They can also try to make sense of the world around them by feeling, tasting, or smelling objects like toys.

At 6 months, they start babbling, and at 9 months, they might make words that sound like ‘mama’ or ‘dada’ and at 12 months, they use other words like ‘no’ and ‘yes’.

An important milestone for infants is developing a sense of object permanence, where they know that an object exists even though it can no longer be seen; like when playing peek-a-boo.

Next, for social milestones, an infant can smile and recognize their parents by 2 months of age. They can copy facial expressions and initiate simple actions at the age of 4 to 6 months; and between 6 to 12 months, infants cooperate with dressing, understand simple commands, fear strangers, and can also feel separation anxiety when the primary caregiver leaves the room.

Finally, there are psychosocial milestones. According to Erikson the infant is in the first stage of development, trust vs mistrust. During this stage, the infant needs physical comfort and reliable care to establish trust in the world around them. On the other hand, the infant will develop a sense of mistrust if they are mistreated or if their basic needs are not met.

Finally, let’s take a look at the main physiologic changes that happen across the different body systems throughout infancy, starting with the nervous system. During the first year of life, infants begin to interact with their environment, and they go through an astonishing amount of cognitive growth in a relatively short period of time. By 6 months of age, the infant’s brain weighs half that of the adult brain. At age 12 months, the brain has grown considerably, weighing 2 and a half times what it did at birth. As the cerebral cortex matures, the most primitive reflex responses disappear, leaving space for voluntary motor activities.

Next, the respiratory system and cardiovascular system continue to mature over the first year of life. The respiratory rate becomes more regular and rhythmic, and slows down from an average of 30 to 60 breaths per minute in the newborn to about 20 to 30 per minute in the 12-month-old. The heart rate also decreases, and blood pressure increases as the heart becomes larger and able to pump more blood with each heartbeat.

Regarding the gastrointestinal system, the stomach capacity is relatively small at birth, however, by 1 year of age, the stomach can accommodate three full meals and several snacks per day. The liver is also immature at birth. The ability to conjugate bilirubin and secrete bile appears after about 2 weeks of age. Other liver functions, such as gluconeogenesis, vitamin storage, and protein metabolism, remain immature during the first year of life. In terms of stools, newborns can have up to 10 stools per day. Breastfed infants' stools are usually looser in texture and appear seedy, but as the infancy period goes on, stool frequency reduces, and the texture and color also change depending on the infant’s diet.