Physical Development in Infancy

Definition of Physical Development in Infancy

Physical development in infancy is the growth and maturation of the body, brain, senses, and neural connections from birth through the first year of life. The term for the period of time right after birth is postnatal. For the mother, this period of time is called postpartum. Physical development happens at a rapid rate soon after a neonate is born.

Physical development involves everything happening inside a baby's body as they go from being a newborn to a 1-year-old. A baby's body lengthens, grows muscle, and puts on weight. The baby learns to use their body in new ways, like sitting up, grabbing toys, and crawling. Babies learn to voluntarily control their muscle movements, and their bodies build up the muscles needed to sit, stand, and eventually walk!

The brain and senses also change during the first year of life. The brain grows in size and builds new neural connections as a baby is exposed to language, colors, shapes, and music. A baby's senses improve drastically. At birth, a baby's vision is very limited, especially their distance vision. Newborn babies go from responding to life automatically and reflexively to purposefully directing their actions, sounds, and movements!

Fig. 1 Infancy, pexels.com

Characteristics of Physical Development In Infancy

There are several important parts of physical development in infancy. These are reflexes, sense preferences, body growth, and brain growth.

Reflexes in Infancy

Newborn babies are born with many natural reflexes crucial for survival. These reflexes are sucking, rooting, swallowing, grasping, and startling. Think about it: a baby would not be able to survive outside of the womb without the ability to eat or consume nutrients.

Eating involves three reflexes that feel natural to a baby. Sucking is how a newborn is able to latch onto a breast or bottle after they are born, and it is a natural part of the feeding process. Rooting is how a baby searches for something to latch onto by turning the head towards food. The rooting reflex is triggered by stroking a baby's cheek. Swallowing is using throat muscles to ingest food. Sucking and rooting diminish over time, but babies learn to control their swallowing.

If you have ever been around a newborn baby, you might have noticed that the baby will automatically close their hand around your finger if you place your finger in their palm. This is the grasping reflex. Newborns are also born with the automatic reaction of startling if there is a loud noise. The baby may flail their arms and legs when they are startled. This is called the Moro reflex.

Fig. 2 Reflexes, pexels.com

Sense Preferences in Infancy

At birth, a baby's vision is very fuzzy. They can only see objects that are 8-10 inches away. This works great for being able to see a parent's face! The rest of a baby's vision is cloudy, but they typically begin to visually follow objects around 3 months old. Babies show a preference for looking at faces over other kinds of objects. By the end of the first year, babies should be able to recognize patterns and colors.

Even though a baby's vision is weak at first, hearing is strong from birth and remains the dominant sense throughout infancy. Infants prefer to listen to their mother's voice, smell her scent, and see her face. A newborn's diet consists of one thing: milk. That milk could be breastmilk, formula, or a combination of both. Infants have a taste preference for sweet or salty foods.

Body Growth in Infancy

Babies develop new motor skills every few months. Typically, they first learn to hold their head up, swing their arms toward objects, and begin to use their hands. Eventually, they can roll over, grab toys, pull up on furniture, and crawl around on the floor. Once babies have enough muscle to hold up their entire body, balance well on their feet, and feel confident exploring, they are ready to begin walking!

While babies are learning new motor skills, their body proportions are growing and changing every day. Weight gain is the main change, but the musculoskeletal system grows and changes as well. At birth, neonates still have a lot of cartilage (soft tissue) instead of bone. Over time those soft tissues are replaced with hard bone that can support a baby's new physical abilities.

Brain Growth in Infancy

How is all this growth and learning taking place? We can attribute a baby's development to neural growth in the brain. On average, the brain of a newborn baby doubles in size during the first year of life. The brain grows in size through neural plasticity: the strengthening and growth of neural connections. The brain literally changes in structure and functions as a person learns through experiences.

Examples of Milestones in Infant Physical Development

Reflexes, motor skills, and body growth should be occurring at a rapid rate throughout infancy. Clinicians and researchers set up developmental guidelines to help parents know if their child needs extra help. These guidelines are called developmental milestones.

Keep in mind that every baby develops at a different rate. Each baby may meet the developmental milestones a little differently and at different times. This is okay! It is normal for each of us to develop in our own unique ways. Opportunities for exploration and a safe, nurturing home environment help support physical development in infancy.

Fig. 3 Milestones, pexels.com

Importance of Physical Development in Infancy

Physical development in infancy results in critical motor skills, strong bones, and important motor development. Babies are incredibly curious and like to explore. Their motor skills help them move around and learn more about the world! In fact, babies that spend time around older children may try to do things the bigger children are doing. Babies are always learning through observing and interacting.

What happens if an infant misses an important milestone, like sitting up, crawling, or grabbing objects? Medical issues or developmental delays can cause issues in achieving milestones. In some cases, brain injuries, neurological issues, or motor nerve injuries impact an infant's ability to thrive.

Milestones stick with an infant through the rest of life. Generally, humans only learn to walk once, and they never forget how after that. After infancy, things like sitting up, standing, and walking become automatic. We do them without even thinking about it. An infant's reflexes go away over time (like startling or rooting), and babies learn to control other things like swallowing.