Infant Nutrition Chapter 8



Child development stages

Skeletal & Muscular Development

Overall growth is probably what parents focus on most during their baby's first year of life. And that's hardly a surprise. Growth is often equated with the health and well-being of infants and children.

According to the Mayo Clinic's Infant and Toddler Health Center, infants generally gain 4-7 oz per week during the first month. After the first month, they gain an average of 1-2 lbs per month for the first 6 months. From 6 months to 1 year, they gain about 1 lb per month.

In terms of length, infants generally grow about 1 inch per month during the first 6 months and about one-half inch per month from 6 months to 1 year. An important indicator is the relationship between weight and length. The ratio of the amount of weight a baby has gained to how long that infant has grown is often the best guage of age-appropriate development (except, of course, in cases where both weight and length are stunted).

Another key measure for infants is head size, which is measured in terms of circumference. At birth, the average is just under 36 cm (about 14 inches), roughly two thirds the circumference of an adult's. In relation to an infant's body, however, the size of the baby's head is huge, accounting for between one third to one quarter of the infant's total length (an adult's head, on the other hand, is just one eighth of the person's height). At 2 months the infant's head circumference is approximately 40 cm, at 4 months just under 44 cm, and at 1 year, just over 46 cm (about 18 inches).

It's important to realize that these are the averages. And parents, of course, can't help but want their babies to be above average. But what's important to remember is that healthy babies come in all shapes and sizes and growth charts aren't tests. Babies don't put on weight uniformly. In any statistical distribution of weight, height, or any other measurement, there will be individuals, whether babies or adults, who are shorter than average, taller than average, heavier or lighter than average. We all need to remind ourselves that there is normal variation within any population.

And at the same time that there is variation in weight and length, there is also variation in stages in the motor and behavioral development, such as when a baby will hold up his head, utter his first word or take his first step. Developmental milestones are averages too, and babies will reach these milestones earlier or later than other babies and still be within the normal range.

Solid Infrastructure

The infrastructure necessary for this growth is the skeletal and muscular system. Nutrition, in terms of both energy and building blocks, is critical. Bone begins its development at six weeks gestation as tightly wound chains of the protein collagen. Minerals from the blood join the protein structure and begin hardening into the extraordinarily strong living material that comprises bone. The complex joint mechanisms that will give the skeleton its remarkable flexibility and range of motion will continue to mature well after birth.

Bone has long been described as superior to a whole range of construction materials, from steel to concrete, in its tensile strength, resilience and ability to withstand compression. The more we learn about it, the more extraordinary it seems. Moreover, it's a construction material that along with the help of specialized cells, can be repaired. What makes bone so versatile is that it is not one material, but a complex combination of many materials, which perform a variety of functions even within a single bone.

Our skeletons would only be static marvels without all of the sinews, tendons, cartilage, and muscles that hold it all together and make possible our extraordinary repertoire of movement. Although skeletal muscles are in place at birth, it takes years for movement patterns to develop and be perfected. Different types of muscle tissue include cardiac muscle and smooth muscle, which is found in the gastrointestinal, respiratory, and reproductive tracts.

Nutrients must support the rapid growth and development of muscle and bone tissue as well as provide energy for motor activity. Protein is just one of the nutrients that are critical to this growth and development. A carefully balanced level of calcium and phosphorus, as well as vitamin D, are important for mineral deposition. Bone and connective tissues also contain many other minerals, including potassium, manganese, magnesium, silica, iron, zinc, selenium, boron, sulfur, chromium, and others. All of these nutrients are transported across the placenta during fetal development. After birth, infants must re-establish the same critical balance of calories and building blocks from their diet.

More on this topic

Infant Nutrition (VIDEO)


Fueling Growth & Development

Milk Enters the Stomach

Milk Enters the Small Intestine

Some Key Nutrients

Gut & Immune Development

Respiratory Health

Skeletal & Muscular Development

Skin & Hair Growth

Cardiovascular Development

The Importance of Fat

DHA & ARA

Nervous System Development

Good Nutrition Builds Healthy Babies

Related Health Centers:


Infant Nutrition Health Center, Mother-Baby Bond Health Center, Mother’s Milk Health Center, Monthly Infant Development Calendar Health Center,Weekly Pregnancy Calendar Health Center


The material on this site is for informational purposes only and is not intended as medical advice. It should not be used to diagnose or treat any medical condition. Consult a licensed medical professional for the diagnosis and treatment of all medical conditions and before starting a new diet or exercise program. If you have a medical emergency, call 911 immediately.